What family secret did you learn later in life which broke your brain?

My grandparents got divorced, both married other people, then both divorced their other partner and got married again. When we ask how long they’ve been together we get two different answers

I was adopted

My mom had a different father than my aunts and uncle. It didn’t really break my brain though because my mom looked much different than her siblings or my grandma 

I did my DNA a couple of years ago and 40 percent of my DNA was from Scandinavia but I don’t have any relatives from that part of the world. I did it a second time and sure enough it came back 38 percent from Scandinavia . No one can explain it. I’ve narrowed it down to my mother’s side but no one can tell me where the Scandinavian dna comes from apparently over 20 percent means a recent family member must have come from there but no one knows who . So I just let sleeping dogs lay and forget about it now.

That there's a small possibility I'm not my dad's kid and all the adults in my family knew that. I was 20 when I found out during an argument