Martin is the son of Random and Morganthe of Rebma, and the heir-apparent (well, apparent to Katarina at least, no one else has ever offered much comment on this topic) to Amber.
He looks as described in the books: a lot like Random, except a little taller and a little broader in the shoulders. He wears a lot of grey and doesn't say much.
Martin is married to Mikele. They have two children, the twins, Alexander & Mira
How to Split a Party of Four People Four Ways The adventures of Katarina, Mikele, Martin, & Nikrowd, with Finndo guest starring as chief bad guy. Read all about it here. (It's long.)
Martin and Mikele's Wedding Their wedding was surprisingly uneventful (the biggest disruption was a shouting match between Flora and Canell), particularly compared to Gilva's.
Martin recently made headlines by scoring a direct hit on the newly crowned Empress of Chaos at her coronation, mere minutes after she had advocated wiping out Amber and seconds after she had felled his wife.