Today i've made a gym subscription because i'm a fat ass and I need to get my s**t together. Anyway, I was talking with the PT and he told me he's married with an older woman (34F and he's 28M) and he also has a daughter. I asked if she was his daughter and he was a bit surprised and said: "Yes, sure is my daughter". I then continued by saying that I asked only because I know young guys like him who are stupid enough to marry a single mother( I phrased it a bit softer). He then told me a story: he basically has friend who fucked (more than once) a girl who's already in a relationship with a guy. He said that this former dude always uses protections but they didn't use any one day and 9 months later she gave birth to a child. The PT also said that his friend really wants to know whether the child is his or of the dude living with her but he doesn't know how to do it without causing damage to a potential family. As I couldn't find a solution as to what he should tell his friend I want to ask you: What would you do in this situation if you were the guy who secretly fucks (or fucked because I didn't get details on whether he's still fucking her or not) the girl?

[We're talking about Italy, if you want to check legislation]