I recently just finished Mean Streets, and am now playing Martian Memorandum. I was wondering about something. From what I've read, in Overseer Tex mentions he was married to Sylvia Linsky. I also know in the beginning of Under A Killing Moon tex's wife cheats on him (I assume this is Sylvia). So was Tex married to Sylvia in Martian Memorandum? Based on the fact that within 3 hours of gameplay he already slept with Alexander's Secretary for info, I can understand if Sylvia was 'revenge-unfaithful" . or did they get married sometime between MM and UAKM?

No, she cheats on him way before UaKM. He's just remembering that particular moment. In fact, he pretty much states that she cheated on him all the time, that was why he left her.
They were probably already divorced by the time of MM.
Production wise, the game makers simply didn't pursue the idea of him having married and divorced Sylvia by that time.

I see. that makes sense. I could kinda tell from her dialogue in Mean Streets that she might not be the most faithful spouse.