I would just like to point out that if he was just asking questions, he might have been genuinely curious. We shouldn't jump to conclusions and assume the worst of someone. Not all men try to "conquer" another after they found someone. Sometimes people are curious and try to get to know you better but some of the questions are awkward to you when it's something they're comfortable talking about.

And even when you're married with some couples they feel that a bit of flirting is okay.

If he very directly came onto you, and it made you feel uncomfortable then say so. Otherwise it's not fair to judge what a person does within their relationship as one does not know what a person consents to with their partner. We should all be careful about jumping to conclusions.