Am I required to care about my boyfriend's grown sons?

I am 41 and am dating a man who's 56, with two grown sons (ages 26 and 30) a daughter-in-law and a grandson. They all live out of state and he doesn't have much of a relationship with them. Am I required to care about them? I don't plan on marrying this man. Oh, and he had a vasectomy at his ex's request so he can't give me the child I want.