Claus would absolutely flirt with dolin. I mean... Head have to be a little drunk to get past his "good boy married man" hangups. Which he probably only would get over 'cuz Sienne gives no shits
Alade would shamelessly flirt with Snake if he knew him, though. The 'Tori-adopting-Snake-as-a-dad' thing would only deter him slightly, and not to the point where it would stop him.
gwyndolin would probably be scandalized if he knew claus was married. but he doesnt. so if he got flirted with in a nice, proper way, he might flirt back....