That does confuse me as well. However, that is not the only thing. Considering that Jaheira was part of the original BG team, she in this game must be about 160-200 years old. She is a half-elf. According to the Forgotten Realms lore, half-elves live up to 120-160 years on an average depending on lifestyle and the type of elf they are.
So, if we accept that Jaheira lived a super healthy life and therefore lived past her expected life span, she still is supposed to be the equivalent of a human woman in her 90s. How is she running around wielding blades? Why is she even alive?
I am also vaguely curious if she adopted those kids? If the daughter is an elf then the timeline might just about work, as elves are not considered adults until around they turn about 100. That being said I think they should still look physically adult long before they turn 100.
I am forever grateful for Larian not openly going with the canon Baahlspawn Abdel “he who should not be named” Adrian from the books, and instead used gender neutral ways to describe them or just called them Gorion’s Ward.