I som t think you should have to unfriend him. Bring itf up with the aprn. See what she thinks.

If it's as simple as her seeing your stiff you could add her to your block list. If she is uncomfortable with you knowingg things aboutf her family tho, that could be different.

I think because you actually know her son, and you knew him before you knew her, that it shouldn't be too big of an issue. You didn't friend him to get a look at her life. You already knew him. That is different.