A baby bat will have plenty of siblings in it's life, but none the same age.
Female bats generally only give birth to just one pup a year. Some belief this is because of the mother's need to fly to feed while pregnant. Female bats nurse their young until they are nearly adult size, because a young bat cannot forage on its own until its wings are fully developed. Infant mortality is high, (if a baby bat looses a grip on its mother or roost, it will fall and die) but bats that reach maturity can live 30 years or more.