I almost ruined my parents marriage when I was 5
How did you almost ruin your parents marriage?
I played with a Barbie doll and I heard them talking about the divorce
As a child you weren't responsible for your parent's relationship. You  were barely old enough to know what was happening.
You might be right, I think I remember them arguing because he wanted to date a younger women than his wife.
See, parents have more problems than their child playing with dolls so you were not responsible. It is their responsibility to be loyal and to talk to each other.