Taru's father, Veeti, was old enough to remember the Rash. And Taru's not old. Also, Trond's parents were adults during the Rash, and he's old but not that old.
Which makes me think, how old were Michael and Signe? I'm not good at guessing ages, especially not of cartoon characters. Given the responsibilities that Michael appears to have had (but not performed), I think he has to be mature: thirties, even forties. But Signe might be younger, maybe mid-twenties. Mikkel was born about Y56, so if she was 25 when the Rash came, she was 81 when he was born. Many people of 81 are vigorous and live into their 90's. If Signe was healthy all the way to 90, Mikkel could have talked to her when he was a boy. Maybe that's why he wanted to be an astronaut: Signe told him about moonshots and Mars rovers.