Je v registrovaném partnerství? (In Czechia we do not have same sex marriage but registered partnership.)
You can also ask. Vzali se se svým partnerem? Did he marry his partner? That will be applicable for the registered partnership, but also for people who married in countries where they have same sex marriage.
Maybe the have some more ways to call it in the LGBTQ community, but the general public will umderstand what I wrote above.