That for me would have to depend on a lot of things. How long have I been dating said boyfriend? Do we plan to spend the rest of our lives together?
But as others have said, the real issue is the lack of respect this guy has for his girlfriend's wishes, especially as they pertain to her children. They need to sit down and have a very serious talk and if he can't agree with her she needs to boot him. I honestly would boot him anyway, because if he's immature enough to not respect something like this, I would have a hard time trusting him to respect my kids, let alone my wishes and the kids come first.