Simon's family survived. Physically, that is.
The soldier managed to get there just in time to save them and also realized that if he wanted to keep his family safe he'd have to disappear. At least for a little while, only until the heat died down.
That took fifteen years.
You watched your dad talk about his brother, Simon. Heard numerous stories about him and was told he was a hero but you didn't see it that way. You saw what happened and how it turned your family inside out. Saw your dad and mom crying, went to your grandfathers funeral without knowing the horrific abuse he put his family through. You managed to somehow blame it all on Simon while still loving him so much.
We all need a villian in our stories but you chose the wrong one.
Now he was here, his family not at threat anymore and it's finally safe to be home. But things are different now, you're older and don't see him the same way anymore.
He doesn't regret what he did and knows that you were and are still too young to understand that he only did this to them all because he had too.
He is sorry he left. It never felt right.