I actually posted this in the "Eagles Radio Sirius Channel 30 November 17, 2017" thread first, but since you guys were discussing it (Timothy's first marriage) here, I figured I'd post the links here too.

In this interview (http://timothybschmitfans.com/otr1101.html) Timothy says:

Yeah, well, during that 13 years, I spent a lot of time hoping and wishing that it would. I was really humbled during that time. My whole lifestyle changed. I started hustling, started, you know, I was singing for people I probably wouldn't normally sing for. I did it just because I didn't want to do anything other than the music. After the band broke up, I was going through a horrible divorce. I lost a lot of stuff. I lost houses. I lost my record deal after my first solo album. Things were just, like, not lookin’ that good, except for the fact that I was with-who is my wife now-I was just starting to be with her and she was...that was the great part of my life then; and we eventually had a child and then a second child.
In a more recent interview(https://www.thesun.co.uk/tvandshowbi...solo-career/):

Next we wind the clock back to ’77 and Schmit’s thoughts on first becoming an Eagle.

He remembers meeting his current partner Jean around the same time and she put everything in perspective.

“My wife and I were just getting to know each other.

When I told her what I did, she was so unimpressed and I found that really attractive.

“She said, ‘I heard you’re joining the Eagles, are you sure about that?’ because she didn’t like them very much.

“But she’s very encouraging of my whole solo thing. She knows it’s part of my happiness. We’ve known each other a long time and we’re best friends.”
So I'm guessing (and it really is just a guess) it was shortly after joining the Eagles that he and his first wife separated, and that he started seeing Jean around the same time.