Is it strange for a 50 year old man want to adopt a relatives baby?

[Annabella]

I have been dating this guy for about a year. He let his sister move in with her baby. His sister goes out a lot and leaves the little boy with him.The sister has been staying with some guy and my boyfriend and his mother have been taking care of the baby. Now my boyfriend is talking about trying to get custody of the child. He has no kids of his own. He never mentions us having a future together and has been breaking dates lately because he is taking the baby to outings and shopping and stuff. I know it sounds like I am being selfish. I work a lot and have my own kids so I am pretty busy myself , but when I do offer to have them join my family,he has an excuse. I have a friend who says I should be more patient and understanding , But I am just getting tired of it all. I could use some help. Thanks.