Ancestry, MyHeritage and suspected Nazis

Some six months ago I dove in head first and started some serious family research. According to an old friend, I needed to kick start my project using Ancestry and then move on to MyHeritage.
So I did. I found a lot of information using Ancestry, I did my DNA on Ancestry and then I moved everything over to MyHeritage.
Unfortunately for me, my DNA test felt a bit like a bust. The close family connecting back in the results are in fact the only known close family I have, and as we all know by now. We’re not that close…

Anyhow. Since my very own close family was a bust I decided to look into the family of my latest ex boyfriend. The reason for this being as simple as his late mother and I shared the same [quite unusual] maiden name.
So just maybe there was indeed an exciting mystery and connection to be found researching this bloodline!
Turns out there was a connection, but not on his mother’s side but many generations back on his father’s side. Where there’s a tiny piece of DNA connecting our families.
How very exciting!
So far so good.
Then I was digging a bit further and realised my ex’s grandfather - the one no one ever mentioned when we were an item - was a military man.
Nothing weird about that, both my dad and his father were military, even my darling husband is ex marine.
But my ex boyfriend’s grand father sure took things to a complete other level.
As we know by now, he was military, but just after the German forces collapsed in the end of WWII this man took his wife and child on a one way ticket to Brazil…
When the man died, the woman ditched South America and brought her kid back to Europe faster than fast.
Need to dig further down into this story, but as a starter it would explain why no one ever brought his name up in any kind of conversation like ever.