You have excellent instincts. Your minor children living with you in a shared custody set up are not the same thing as his adult child and her husband and kids living with him. He’s got a life style that is incompatible with what you want, and frankly, step-children and adult step-children can be the same relationship impediments that mothers-in-law have been known to be. Your boyfriend’s relationship with his adult daughter needs to be secondary to his relationship with a significant other who may become his wife if he wants that latter relationship to work. I don’t think your boyfriend is ready or interested in that, and I think that as disappointing as that is, it’s better for you to move on and find someone with a compatible lifestyle, shared values, and shared goals. He’s probably great, but this is a deal breaker. You can love him, but I don’t think you can live with him.