The thing is that as much as parents think they conceal things, they often leave their kids in a position where they know they are being lied to or excluded from the truth and consequently are reluctant to ask. My son knows my friends because we have a wide but close knit network so new people stick out.
My son has met my current partner as a friend. I worked hard to make sure I treated him like a friend. I wasn't sure it worked until he asked me when I will get a boyfriend and if im a lesbian now.