Just some questions if that's ok, so I understand this better.

He had sex with his aunt "a couple of times." How old is he? Was this recent or like during teenage years??

And sorry for the next question but was protection used? Bec if you plan to have a physical relationship with him it would be nice to know.

I'm also not sure why someone would say they had a terrible secret to someone unless they wanted to get this secret off their chest.
What do you wanto do with this information? Has he given you any background information about it?