I really tried to treat them fair at first, but SD started causing drama, BM would get jealous and complain about petty stuff, like taking SD to story time at the library, and SD would make sure she had 100% of DHs time & attention.  On top all of it she’s not a likable kid.  She’s loud, selfish, manipulative, and mean, and DH lets her act like that.  She’s a hassle to take anywhere or do anything with.

One day I realized that SD has two very dysfunctional and over involved parents and really my kids only have me.  So I dropped that rope.  I am my kiddos only mom, and I am going to be the best mom I can be.

My MIL has taken SD on many many secret shopping trips where my kids couldn’t come, and brought SD home with candy and toys, and none for mine.  She missed my kids birthdays, but if she gave them something on their birthday SD always got a bigger and better present on their birthday.  The thing is my kids blame SD, not MIL.  We keep visits to a bare minimum, like once a year, as a nod to her birthing my DH.

We had our son (13 months) when SD was 5. We have full-custody of her and have had full-custody since she was 2 - her mother has visitation. 

My husband doesn't treat them differently, no. If anything, I think he secretly prefers our son because he's in love with me, and he's been able to be involved heavily (whereas with BM he had to work constantly to afford everything because she refused to help financially - quit her job a few weeks before she would have qualified for maternity leave pay which is 55% of her salary for a year here) 

He would never say it or show favoritism but I think he does prefer our son. Both kids are treated fairly, though. My pregnancy was more exciting. By the time BM was pregnant, their relationship was already going down the drain and he didn't like who she was so he wasn't as excited or "close" to her throughout. I told him beforehand I couldn't deal with him treating it as a "second time" thing, even though it was. He understood and acted like everything was new to him lol. 

Even at the ultrasound, when they'd ask if it's our first child, he'd smile and say yes and wink at me, which melted my heart. For the first 6 months or so, SD was really jealous and wanted all the attention. He told her that's not how it works - baby is smallest and needs the most attention and that's just how it is. He totally understood that that's the way it works in an in-tact family. Baby takes a lot of time and attention - older kids have to suck it up and even help sometimes. 

We consoled her as much as we could but we didn't give into petty or jealous outbursts. We would have her go to her room if she was being overly jealous or needy. Example - we threw the baby a little "half birthday" at 6 months to celebrate his first food and all - she got all sad and upset. He sent her to her room and said she can come back when she's ready to be happy for someone else's accomplishments, just like we'll expect him to be happy for hers as they grow up together. 

As for the in-laws... SD was the first grandkid/neice/nephew on my husband's side so I do feel she gets special treatment sometimes. But the oldest grandkid in my family (my cousin) also got special treatment and we're all in-tact familes so I think that's normal. 

For me, pregnancy with our first daughter (3) was terrifying and exciting and unexpected.  Terrifying because when I became pregnant I was contemplating leaving because of his family, the skids, and ex wife and felt I would be stuck in Hell forever.  I didn't want ANY of my kids raised dealing with Skidz who had serious behavioral issues.  It was exciting for obvious reasons, and unexpected because I was told that due to an IUD issue I wouldn't be able to become pregnant and had not been taking precautions for two years and hadn't become pregnant.  Vitamin D and baby aspirin (who knew) caused the increased ability for implantation. So, when I found out I was stunned, confused, in disbelief, excited, and terrified.  The day we got married, my sister-in-law threatened me that if I got pregnant she would kill me because "DH already has enough on his plate!"  We had discussed the possibility, but owing to his previous relationships, and experience he was hesitant.  When I told him he was happy, and said "yeah, I knew it!"  Then kissed me.  I felt guilty.  Every night during my pregnancy I would wake to him talking to my stomach.  Saying things about his day, how much he loved Mommy, how beautiful the baby was going to be, etc. it was really sweet and special, but we also struggled with telling his family.  His Mom in particular.  When we finally had to, she cried, and decided to leave for Australia for a Mormon Mission for two years.  It hurt a little, because she had been present for every delivery of a Grandchild, and I wanted her to be involved, but she wanted nothing to do with it.  His Dad, My FIL, adores our two little girls and is very attached to our littlest.  My MIL?  Well, my DH and his Ex BM we're together a total of 5 and a half years.  They have been divorced for 7, and we have been together for 6.  He had a friend with benefits BM before his ex.  In my MIL home there a great deal of pics on the wall, but you will NOT find one of me.  You will NOT find one of BM number 1, but there are a total of four of first wife and BM #2.  Why?  IDK?  My FIL Loathes BM2.  His sisters claim to loathe her as well, but they all have photos of my children's Daddy with another woman on the wall.  I receive praise on occasion for my undying and unending service to their Grandkids, and I receive the responsibility for the. Endlessly, but as far as the credit?  Or gratitude for my babies?  Yeah, forget it.  When I went into labor and she had to watch the behaviorally challenged Skidz, she called every hour complaining that I wasn't done yet, and the minute (literally minute) I was done pushing, she was telling him he could leave now.  She was pretty horrible to me as well.  I cried and had to have nurses come in to comfort me.  Then there was the photos.  The photo of his ex wife and him cuddling in the hospital  bed together holding SS 11 and smiling after his birth, surrounded with both sets of Grandparents and others and a barrage of gifts and flowers.  I have iPhone images of just me and baby, and just him and baby, and in his photos he's watching TV, and I am happy, but alone in the bed (and I was WAY smaller than her when she had the baby so that wasn't it).  Those still haunt me sometimes.  It hurt. Since then, Yes, every major event has been less special if it involves my bio kids vs Skids.  Skids birthdays are major events, their Illnesses and injuries bring the entire family out.  My SS 9, fell on playground equipment at school.  He smashed out his front tooth, and cut his lip.  I took him to the ER (because BM was off screwing his attacker and her pedophile bf).  I sat for seven hours with him, then she shows up and brings my in laws, her family, and everyone there to pray for him because of his stitches.  Now, don't get me wrong, it was not a good day, and he was seriously hurt, but his injuries were NOT life threatening.  My 3 year old was hospitalized at 2, with CHOLERA!  That's right, Cholera, and they told us on day 2, she may not make it, and NOT 1 of my husbands family members ONE came to the hospital to visit in the 10 days she was hospitalized (and her Dad didn't either).  I almost got divorced the day I was discharged to be honest.  That said, I didn't continue in my pregnancy for them.  Not even for my husband.  I actually did co template termination, but I fell in love.  I loved her, and wanted her, and praise God for her and her 1 year old baby sister EVERY Single Day!  I would do it all again in a heartbeat, and to me, she and baby sister are main event.   They are the reason why any of it is worth it.  

First off let me say that just bc others have had bad experiences, that don’t mean you will. How your DH/inlaws reacts and treats you and your child is up to him/them. 

Here’s my negative experience. My SO has a child from a previous relationship, we have 2 together. I my first pregnancy when I was anticipating labor and delivery, he let me know his ex had no problems “3 pushes and she was out, no big deal”. Whatever, I could care less about her experience and the birth of your spawn; this is me, I am nervous. He told me things he did for this child before her birth, such as start a piggy bank for her. Did he do this for our children, no. It was like pulling teeth to get him to come to any prenatal appts, even after I tried to schedule around his work & SD’s visitation. I was legit concerned that he wouldn’t even show up at the birth if it was his visitation time with SD (he has 50/50). After the birth of the first LO he did nothing to help and I had to end up taking meds after being up all night & walking the floor with our newborn. 

Fast forward, he still does not attend any dr appts or well child visits with our children. Our youngest is 1, he hasn’t been to 1 appt. Lucky for me, my mom goes to help. He did pick up SD from school and take her when she was sick. He would not take off work for a specialist appt out of town, yet a week later he took off for a school program for SD. He has talked about how hard it was to be up at night with SD when she was a baby then get up for work the next morning; he has never got up with our children throughout the night and actually sleeps in a different room after the first one came along. He talks about bathing SD as a baby; he has never bathed either of our children. I cannot hang pictures of our children in the home, unless there is an equal picture of SD hung. I have been told i am trying to interrupt his time with SD if I ask him to help with our children while SD is here. SD does not have to follow the rules of the home, unless I enforce; and then I am “trying to change her”. If SD is at his home on visitation, he will not go do things with our children (ex., on 4th of July he refused to go with our family to watch fireworks bc SD didn’t want to go and he had to be with her). 

MIL was not at the birth of our 2nd bc it was visitation with SD. She has gone weeks without seeing our children; however SD is at her house almost daily when she is here on visitation. She has purchased, gifts/toys/clothes/etc. for SD and not for the others. SD has picked up on this and has made it known that she gets bigger/expensive things “I got a bicycle and it was $80”. When SD got sick at vacation time, vacation was canceled. When our child then got sick, it was that’s awful but we’re still going. To say the least, there is a huge difference. 

Sorry for the long post. I sincerely hope your experience is a good one. 

I know I already commented a novel up above, but I thought I would throw in a few thoughts that may directly help you.  First, pregnancy makes us quick to become emotional.  I would wait before making any divorce decisions, unless it's an abusive situation (then RUN).  Second, it took me five years of marriage to get to the point of understanding that I had a right to spoil JUST MY KIDS!  It sounds so sad right?  It's not.  Children of divorce are often looked at as having this horrible life that needs to be made better.  The reality is, kids are smart.  My Skids always destroy property, or fight the most, etc the day they go back.  Why? Because they don't suffer consequences.  BM lets them off for everything.  My Skids have my MIL and FIL and an army of Aunts and Uncles showing up for them EVERYWHERE.  They have their BM Mom and StepDad and Her BioDad and StepMom and an army of Aunts, Uncles, and Cousins.  My children?  Well, they have each other, and me and their Dad.  My parents are dead, my siblings were old enough to be my parents and live elsewhere.  So, when the Skids go home for Christmas December 26th, we have second Christmas.  When they go home for the weekend, we have fun weekend.  For a long time my DH wanted to suspend ALL fun activities and Holidays until the Skidz were home.  That stopped two years ago to some degree when I basically said "enough, you can wait to enjoy life, but my babies and I are not going to, and we will have fun without you."  And completely ended 1 year ago when I allowed him to realize (by spending a week alone with the Skidz with no help) that it is actually MORE fun, LESS chaotic, and WAY LESS embarrassing to go out to places without kids who fight and scream everywhere they go.  By fight I don't mean bicker.  I mean ramming each other full force with grocery carts and then the other screaming.  That kind of fight.  By yell, I mean yelling every word they utter.  (Their Mom is an attention seeker who can't speak at a normal decibel).   So, just do you and your little one.  Trust me, your DH May even realize what it's like to have fun with a wife and child that isn't embarrassing, childish, or crazy, and find himself suddenly happy again.  I'm looking forward to second Christmas, and I'm sure you will enjoy your sweet baby as well.  

My SO has 3 older kids and he never once seemed distant during my pregnancy. He was very excited to have another girl and doesn't at all treat her different from the other kids. Although I wouldn't say he treats all his kids the exact same.

That's something we have had to talk about. But he's a good dad.

The in laws are great. Very supportive and excited in general to be around the baby. To them it's an extention to the family and something to be happy about.