For me this would be a dealbreaker. If your BF refuses to get his son help, and doesn't believe in counselling anyway, that child is highly unlikely to spontaneously see the light and become a model child. If you stay together this is the best it's going to be, and could be a deal worse.

--"We have full custody of the 15 yr old boy"--

No, "we" does not. Your BF has custody of his son.

--"He asks if he can move in every couple weeks and I say no and we fight, he says I hate his son and am keeping him from him."--

Seriously, what's to fight about? Your BF has custody of one of his sons and the other one seems to need his father just as much if not more. YOU aren't keeping any troubled teen from his father, BF is doing that all by himself. BF has chosen to put his love life before his child who is in dire need of professional help and guidance from his father. BF can move out, rent a home/apartment and have his other son with him 24/7.

--" I feel my boyfriend resents me "--

All the more reason to realize this guy is not concerned about what is in your/your daughter's best interest...it's all about 'me me me, what me wants, what me needs'.

--"he promised he would get his son help and he didn't"--

Even more reason to realize BF 'sees' no problem here except for the fact you aren't giving BF his own way and in the name of 'but I loovvvve him'.

None of this is anything that you're going to 'move past' and everything is going to be just fine. What you're stating here is not mild blending family issues that hopefully smooth themselves out. You're talking about a very troubled teen, a possible real danger to your own daughter's heath and well being (not to mention what has already occurred to her), a guy with his head in the sand who blames you he's not a responsible parent (getting his son help) and tries to manipulate you into getting his own unsafe/unhealthy way (just letting teen move in 24/7 to expose your daughter to teen all over again)...no, these are not blending family issues that are all going to poof all in the name of 'love' you have for this guy.

what justmetoo said.

Love isn't an overwhelming, crushing, tsunami that leaves us powerless in its wake, unless we're 14 years old & the Beatles are on Ed Sullivan, but we outgrow that.

Love in the real world (the world of sexually aggressive/sexually abusive sons for whom a father is responsible & scared & abused daughters for whose safety a mother is responsible) is a *decision*, & we can change our minds.

We can make a new decision.

My own children are grown and married. I married someone who has teen children. Two daughters aged 12 & 16, and adopted son who is 14, and came to live with us after we had been married a year. My husband kept it from me that the mother wanted this child out of her home because he elbowed her in the stomach and slammed the car door on her arm when he was 10. The reason being the mother would not buy him a stuffed animal from Cracker Barrel.
The kids are still the bigger problem, but the husband is an enabler for the disrespect and behavior. I started in counseling in March to figure out what I wanted to do about this confusing marriage. My counselor told me, that you should have called CPS to protect your own child, and CPS would have handled this out of bounds, renegade son of your partner. What transacted is indeed very serious.
My experience can tell you your situation is going no where. Raise your own child first, then seek out your companionship. Even in that event it may not work out, then you will still be better off because you protected your own child. You do not have any control over how his son acts, you cannot control the fact that your partner wants him around. I will tell you the kids will always come before you, probably even after they are adults. I just had something very valuable stolen from the home. My husband is acting like it is "no big deal." And why should I call the police to report a burglary, and speak to the boy about what he knows about it? I should suck up the $2800 loss, and forget and live without it. Does this tell you how the events will go in your life in the future?
Right now, I am trying to find a home, so I will not have to move my belongings twice, that is why an apartment is a last resort for me to consider.

and it's our only issue. Is it impossible to move past?? :(

Sadly, yes, this is impossible to move past. Because to your boyfriend moving past means moving that boy in and pretending it never happened.

Your daughter must come first. Please do not allow yourself to be bullied and browbeaten into going along with any plan to put that boy in the same house with your daughter.

Since your boyfriend has shown he's unwilling to protect your child or get his son the help he clearly needs, your best option is to get out of there.

No. Dealbreaker, just leave now. Your daughter must be your first priority and I think you know in your heart this just can't ever work. His son preyed upon your daughter. He is sick and needs help.Your BF is not thinking of how this affected you or your daughter.

Why set yourself and your daughter up for a life of fear in your own home? Either leave or tell him to leave. Show your daughter what a strong healthy woman does when her child is victimized.Teach her how to be strong and never accept being a victim. You can do this.

(((Hugs)))
~Cat

Just another example of why my GF and I have chosen to NOT blend our families...not like anything this extreme would happen, but life is so much simpler this way.

But how the OP can be in love with a guy who refuses to get his son help and allows her daughter to be in a dangerous situation is beyond me....she needs to get the hell out of there...

Leave this will not work don't allow the boy around your daughter much worse could and probably will happen to her if this boy is around her!\

"But how the OP can be in love with a guy who"

I don't know how it happens, but it happens all the time;
just watch the news.

Kristi, you've been given excellent insights & advice.

Please get yourself & your precious daughter out of there.

A man who refuses to control his sexually aggressive son is enabling that son to assault (rape) your daughter.

I wish you the best.

I agree...get out!! You can not move past this!

The most important job you have is caring for your children. You put them first. The boy is sick and he will never change and may become dangerous when women reject him. He could end up being a serial killer, this is the way most start out. It may break your heart to leave now, but it won't be near as hard as knowing you were responsible for her being harm, mentally and physically. Get her out of there now.

I don't understand this kind of crap, why are women so desperate to have a man, any kind of man. Seems like every six months or so in my state a baby is killed by a BOY FRIEND. What's wrong with these women. In most cases there were previous warnings, bruises, etc..

So sad but you have to understand, the son doesn't see your daughter as his sister. She is another girl his age since they don't have that sibling bond. You worry about never liking his son - did you ask yourself if your BF likes your daughter enough to protect her?

We are all very defensive and a bit blind when it comes to our own children. We also get embarrassed about bad behavior from our kids in front of other people, especially the person we love and want to impress.

The others above are correct, you have to get your daughter out. It may be better to continue dating your BF but having separate residences until the kids are out on their own. If you are meant to be with him, it will survive living apart. What a relationship won't survive is constant friction and resentment.