Around 77 years old is normal especialy if you play in the Nature faction. It's the everage for my tribes too, I just have 5 or 6 that died at 80, and 1 at 85!!
I don't know if I'll reach the 90 one day!

For the triplets, it's random and you'd have (highlight the following for spoiler) the level 3 of Medicine (end of spoiler)