Same boat as you. My DH does anything for my adult kids...looks for opportunities to help them or bond with them. They both live out of state so they are independent and don't require much.

His kids are entitled monsters. I feel bad that I cant stand them.

My kids are successful adults. His kids are liars manipulative, victims and mostly headed for loserville. My kids are more likable. Not just saying that as their mommy. I mean my step kids were abandoned by their mom because her boyfriend wouldnt put up with them so they live with us now. They're disgusting.

Im the definition of wicked step mom.

I feel bad for the kids but still cant stomach them.

Sadly, unless BM and your DH can come to an agreement on screen time allowances, physical activites, ect- he won't change. I am really surprised that the doctor isn't recommending more physical activity (he/she probably is and BM makes excuses for him, I am sure). 

Maybe you guys could spring for a YMCA or rec center membership. Maybe wed nights can revolve around a excecise class as a family- kick boxing, Jungle Gym, Swim (my sisters Y has an aquatic track and her and her husband love), etc. Then a Saturday class too when he is with you guys. Get healthy together and bond over it? I don't know... Just a suggestion. I have one Skid who is autistic and bi polar and my BS13 has severe anxiety- exercise is good for them and actually helps meds work better. 

It's tough when your SO has a child that you don't particularly click with.  I know I definitely had a less than warm and fuzzy feeling towards my SD's older daughter... she was just.. odd.. I guess.  It's not that she really did much that was out of the ordinary bad.. but she just reminded me of "Tuesday" from the adams family.. the girl just seemed to have very little inner joy.  She was just morose.  She also grew up to be extremely materialistic.. and focused on her appearance and having the 'right" clothes.  We literally spent a week trying to find the right shoes in the right color in her oversized foot size..lol.  She just wasn't very interested in interacting with me..

I guess the best way to deal with this is see him as a human being as opposed to the sum of his "disgusting" parts. To an extent, he can't help but be who he is.. and how he was raised by BOTH parents (your DH is half him).  And.. while he may have some negative traits.. perhaps there are some things about him you could find to admire?  Maybe he is good at art (my older SD was).. or good at math.. or maybe he is good at strategy (on his games).  Focus on the good.. and the fact that all  kids are different and perhaps his parent's split was harder on him.. maybe changing homes is harder on him.. maybe he gets bullied at school and eats for comfort?  Look for ways to empathize for his situation. I'm not saying you will "love" him.. but maybe you could at least see him as a human being and imperfect as we all are in some way.  I mean.. some people might say that you are overly hung up on physical appearance without taking into account that not all people are heavy because they are "lazy".. in fact there are usually very complicated reasons why people overeat and gain weight.  My OSD used to say snide things about other people we would see out if they were heavy.. wearing a bathing suit.. or wearing clothes that looked too small.  "She shouldn't be wearing that". etc... I (in the nicest way I could) would ask her if she knew whether that person could afford to buy bigger clothes.. does she know if that person has a health problem..or is dealing with abuse.. or is working a desk job to support her family and has no time to eat right or exercise.. or maybe she is depressed.. so are you telling me that all fat people should just hide in a dark room and wear full coverage parkas in 99 degree heat so you don't have to see them?'  After a while, she learned to either be less judgemental.. or maybe just learned to keep her mouth shut around me..lol. 

There is also nothing that says you can't encourage your DH to help his son work on some issues.  you approach it with your concern.  "I'm worried he will develop diabetes if he continues to gain weight.. I'm worried about his ability to make friends if he is bullied.  etc.. "  That's how I worked on my DH's parenting with him. from a place of caring and concern for his daughter's well being.

Then there is this final tool... "fake it till you make it".. pretend.. use positive affirmations about him.. tell yourself your attitude is positive.. and just polly anna away at it.. until maybe you actually believe it?

I struggle with this as well.

First I’d say, stop comparing him with your kids.  Ive done that too, it doesn’t help, and that really only makes us feel better about ourselves.  It’s very not fair either, he’s got different DNA, a different background, and a different personality with different interests Of course he’s not going to be similar to your kids.

Feel sorry for him.  He doesn’t get good grades because his parents have low expectations. He’s overweight because his parents don’t force him to get up and out or eat well.  He lacks manners because his parents haven’t instilled them.  Really you should be mad at DH and BM, they’ve done their child a huge disservice, and now he’s really going to struggle in the world.

Maybe see his video game habit as something not that bad, he’s not hurting anyone, and some people argue that video games can teach kids skills.  Or that lots of not good at school people (like Thomas Edison or Einstein) became great contributors to our society.  Or that some 80% of our population is overweight, it’s not that big of a deal.  

As for the manners, I had it out with DH about SDs manners, over and over again.  To me, kindness towards others should be the #1 trait anyone should have, if you don’t have that, nothing else matters.  It’s to the point where she has no friends.  It has gotten better with his coaching, she’s more social, even at home now, which is nice.

I’d also find opportunities where you can be kind to your SS, maybe buy him a small gift, or praise him at something, but make it genuine, he’ll pribably be able to tell if it’s not,  and remove yourself from situations where you just can’t feel kind towards him.

I think you should try to support your DH for a few hours with his DS.  You should plan outings, fun things with some physical movement as paintball, type of thing. It may be good for all three of you.  But I did say a few hours EOW. 

You are not going to change BM or SS.  The craziness is only going to get worst the closer she gets to losing the CS money.  You just have to deal, with SS for a few hours a month.  Go out, do something when SS is there. 

My kid (former SKid-26 adopted at 22 by his request) has been dragging his mom and I all over the place all day shopping for gifts for his grandparents.  

These are my parents.  The most dedicated and loving GPs in his life.  If he were toxic, they wouldn’t be the most dedicated GPs.  

Behavior counts.  Dedication is rare if it isn't earned.

I totally relate! Ugggh my ss is 12 and a lazy sloth.  Everything is boring, so he just flops on the couch to sleep as his way to say Fck you to us! We have him every other wknd, and zero wifi for him, so his way is to sabotage things.  I literally hide out, (as I am doing right now!) His BM is totally the issue. She is supposed to use the support $$$ she gets for activities, but she hasn't enrolled him in anything for 2 yrs. So he lives on video games at her place. I am so frustrated and feel your pain!!! 

Oh, and she just bought him a phone for his bday.  So now he has another screen to keep him occupied. Although he has zero friends, but lives on YouTube.  Not.my.kid.

I'm a firm believer that occupation does't mean squat. My SD16 does sports year round, active in her youth group, keeps her room clean, and gets perfect grades. She's also incredibly shallow, conceited, and enjoys being a bully to even her friends. She lies, steals, and cheats. Says she gets good grades so she can get a good job and get away from us. She likes to put down her older brothers who both didnt graduate from high school. 

I would take a child that cares about others and has compassion for others over a narcissistic college graduate any day. It would be nice if I could have both but it doesnt always work out that way. I try to parent the kid I have and not the kid I wish I had. 

You might just be too different for your SS. Have you ever thought about talking to him about his video games or try playing a game with him  eventually you could work in some other more positive activities.  Yet he isnt your kid so if you dont want to thats fine too. 

I got poor grades. I'm ADHD. Sports was what I was good at but if we had all those video games back then I would of probably been hooked on them especially if I was overweight. Kids don't like to be overweight or get bad grades. Video games is an escape. Stepping out of that comfort zone for a kid is terrifying and near impossible if they havent learned other skills to do things differently. 

Hope I didnt sound harsh. If I did it wasnt my intention. I don't know if there is an easy answer for your situation or even anything you can do about it. Without DH on the same page it sounds like a losing battle. Maybe make your expectations smaller at first. Find an app that he can gamify his chores like Habitica. He can get points for things like making his bed that help him move up in levels and buy things for his avatar. He can do battles, challenges, and even socialize.