You aren't. This needs to be reported and addressed while he is still a minor. If he gets caught at over 18, it's prison and sex offender registry (though that may be where he belongs.)

You need to do whatever it takes to protect your kids. Whatever it takes. 

You're not overreacting. It's best that this be addressed while he's still a minor.  Also, there is no way I would have my daughter in the same home as your SS.

As you've informed his therapist, this could well be out of your hands soon. I'd have been out the door the day I found out that he was stealing your daughter's underwear. 

Report it before it comes back on you. Two therapists know about it and, even without that, the police catch up on child porn offenders sooner or later and when it comes out that you knew and did nothing... You could lose your daughter. So, yes, report it.

cut off all access to the internet for him from your home. if his searches are on your system then it's associated w/ your home. Your family can be torn apart by his searches. 

Either SS moves out or you and your daughter move out. There is no way this kid should be living in a home with an unrelated child. Your first priority is to protect your daughter. SS has two parents who clearly don't care about him and you can't care more than they do. You are not in any way overreacting.

OP, I just read that you have an 11-year-old daughter and a 13-year-old son. Ideally, your DH can see SS outside your home. If he lives primarily at BM's, maybe BM can keep him full-time, even of it means more CS, and your husband can take him for day visits or stay in a hotel with him. Ideally, though, SS gets some kind of inpatient care. Hospitalization then a therapeutic boarding school maybe.

Not to alarm you (ok, well, maybe you need alarming), but near me, a 19-year-old was just arrested for killing his mother and her dog. The charges included murder, cruelty to animals, and aggravated crimes against nature. There is much speculation as to what led to the last charge, and what signs, if any, there were prior to this incident. I would imagine the signs were similar to what you are experiencing. This kid has shown a predilection for sexual deviance and also *violence*. That is a bad combo. 

To visit child porn web sight. Not legal. The government check inter net uses   They will be raiding your homes  by our internet provider will turn over the records   This kid needs to be in a home not your house. Or living with his BF in a no tell hotel 

'If he wants to wear woman's cloths. Take him to a second hand clothing store and buy him all the woman's clothing he wants along with bras and panties. Let him stay in his room and get his rocks off.  He getting them off anyway. Let him be happy.  You will not be able to change him.  The DR's aren't doing anything  Brfause they can not change him 

He is most likely not taking his medication  BECAUSE these meds stop him from getting his rocks off. 

But see paragraph 2. Where he with BF in a motel not your house.
 Seriously you MUST protect your other kids BD. She should not be living like this because you married a loser with a bigger loser kid   

As a survivior of childhood sexual abuse, your SS is quickly becoming a predator. As others have said, I'd have left that home a long time ago as I allowed NOTHING of that matter to be near my bio babies/children. Your SS is sick and his father (your DH) has his head in the sand with his kid. I'd say the BM, too, but it seems like she's trying since you advised her of the issue.

I'd report this to his therapist and then your DH would see his son outside the family home or I'd make plans to move out with my kids. Above all, protect your children. This kid is dangerous. And remember, your children are minors. If this behavior comes out to authorities and they find yout you knew about but continued putting your kids around him, CPS could take your kids away. 

What a mess. Get yourself and your kids away from this predator.

You have a daughter and your ss is stealing her doll and undressed the doll, in top of stealing yours and his mothers undergarment. AND he was searching for child porn.

i don't care if he has ADHD or autism, he is posing danger to your children. Please act now! I too have a daughter and an autistic+adhd ss(16) who is into porn now, but he at least has not been looking into child porn and has not been stealing anyone's undergarments. The moment ss is any threat to my girl in any sexual way, either he will be out or my girl and I will move out. There will be no second chance.

"Bio mom and dad say that this kid was doing that because his maturity level is that of a 10 year old."

I found it particularly troubling that both parents seemed to consider it "normal" for a 10 yo to be searching for and looking at kiddie porn. It is in no way normal. Not even slightly.

For sure, get an RO/PO and keep this kid the hell away from your 11yo daughter.

If his own parents are so delusional as to not assertively deal with this child porn loving future felon, that is on them. 

You have to pretect your child from their breeding nightmare.

Special needs of not, this is not acceptable and represents an ongoing failure by daddy and mommy.  Do not make your own child the sacrifice on their alter of failed parenting.

Report the perve, get the RO/PO keeping him far away from your child, your home, and any other children.   

To protect yourself, end this dangerous relationship. It puts your daughter at risk and puts you at risk of losing her if you do not act immediately.

IMHO.

Ma'am, where is your 11 year old daughters Dad? Does he know about his daughters step brother? Have you been fully transparent with your ex?

Forget about your husbands son you said the therpists are compeltely aware of everything he does---YOUR focus has always been and must remain, the protection of your daughter. GET her out of there. 

That is your obligation as a parent.

The number of sex offenders and even murderers who showed a predilection for women's clothing/undergarments from a young age is both impressive and terrifying.

You've been around your SS for a good while, so you may have been a bit like the frog in a pan of water on a stove - not aware of the escalating danger. Well, the rest of us are jumping up and down, yelling for you to take action. Your highest duty is to protect your children - in fact, you should be having individual convos with them to find out if anything has ALREADY happened to them. You also need to take steps to protect yourself in the event CPS gets involved - which seems likely. You can't unknow what you know, so please do whatever you need to do to keep SS alway from your bios.

I think we've scared her away ...

but #1- you aren't overreacting.  #2- if you have a child also living in this house they are not safe.  #3- you may not be safe living in this house.

These are concenrs are both extremely valid, and urgent, and you need to have addressed to your satisfaction.  After discovering this if something were to happen at your houes to someone else, it would be hard to blame anyone but yourself.

I know it's an old post and the original poster seems to be long gone. Hopefully she's done the right thing by her kids and chucked the whole future convict and his father overboard. But I thought I'd comment, as this is sadly not an uncommon scenario. Most CSA is perpetrated by other children. When it's 4-5 year difference, it's considered paedophilia, and most paedos don't acquire their interests in their adulthood. This kid with the combo of his developmental disorders, appetite for violence and sexual interests is very, very bad news. It'll only get worse as with every offence and being let off (by parents - due to their ignorance, by authorities - due to his disability) he'll become emboldened and convinced of his impunity. 
I have unfortunately ran into those types through work before, in their early adulthood. One had a history of assaulting his sisters growing up. He was also a scary looking ogre with predatory teeth. His father had some weird religious obsessions, and always tended to downplay the damage he had to to his sisters, and would tell me at length about their amazing interstate trips (him and the son in his 30s, the mother was dead by then) every Christmas they'd have to visit the daughters. I can only imagine they were too damaged by trauma and too terrified to say no. This guy lived in a home and was continuously seeking out children, even attempting to carry some away from parks in front of mothers. Nothing ever happened to him because he had a degree of mental retardation, but he knew what he was doing - trying to make up some bad lies afterwards or run/cover his tracks. Thankfully, he's dead now, finished off by one of his disorders. 
 

Another one was in his early 20s, also living in a home, with another young man who was severely disabled and didn't speak - he was the former one's literal punching bag. Staff didn't care, they all wanted an easy shift and were also scared of the violent guy. This dude had spent 2.5 years in jail in his late teens for assaulting his older sister. His mother was highly educated and would talk about his sick ongoing internet search interests, attempts to lure kids through social media as symptoms, difficulties he had rather than heinous, vile habits. She was more concerned with "reconciling" her daughter with the son, to the point where the daughter agreed to have this scum at her 20th birthday. Again, I don't understand this mother's reasoning and can only be sad for the daughter. The last I saw him, he was continuing down the same path, attempting to use sexual intimidation on any female around him, including his physician (me), not that it worked. 
 

For people like this, there's no return. The only thing that the families can do is throw them out to services and protect their other children as early as they can. Anything else is enabling the predator.