Thinking about Nonnie's point, as I understand it - If a child's parent dies and the remaining parent estranges them from the deceased parent's relatives, then the child may not be told much about that part of their heritage. It's not necessarily the case but very likely. Unfortunate, I agree, but not the end of the world for the child. As long as they are brought up in a happy, stable home they will probably be ok (not talking about the loss of meaningful relationships here, just about the loss of connection w/ a heritage).
However, today, it is easier than ever to learn about one's heritage. It may not happen till the child is older, but, if they're interested, they can learn about the "missing" heritage online, via books, etc.
In fact, if they are so inclined, they can search out their dead parent's family tree online - and sometimes get more - and more accurate - information than they would from relatives, LOL! Is it nicer to learn all this from the people, themselves, and hear family anecdotes, etc. Yes, I think so. My point is just that they won't miss out on their deceased parent's heritage entirely if they don't have contact w/ those relatives.