Aunt/Uncle same age as you?

Has anyone had an aunt or an uncle who was the same age as you? How did your relationship go growing up? I just had my first baby and my mom just found out she’s pregnant with her 4th kid. So her baby will actually be younger than mine. Do you think they’ll have a strong relationship, like probably more cousin like? The only thing I can think of is her baby trying to act like the boss when they’re older because they’re the aunt/uncle lmao, and since they’re my sibling I know for sure they’ll have that attitude to do it.