<human>: Can you provide a brief rundown of the text in within 3 sentences?

I'm a 27f, my SO is 26m. His mother is 50 and his ex is a 24f. 
My SO and I are currently out of the country teaching, so I'm not worried about him cheating or anything, and wouldn't be even if we lived in the same place. 

But when he calls home to his mother she tells him about how she went for dinner/hiking/breakfast/coffee etc. with his ex gf. They broke up 2 years ago. We 've deen dating for almost the same amount of time. 

I understand that they (the ex and his mother) were close when my SO and this girl were dating (they were together 4 years). They have a lot of interests in common as well. His mother is also going through a divorce right now and apparently doesn't have a lot of friends her age to confide in or spend time with. 

Maybe I just feel jealous since I've never really been able to get to know his mother on a more personal level since we don't live in the same country. 

My family has a lot of disfunctional aspects as well. But I can't help but feel uncomfortable by this. My SO knows I think it's weird and he did too at first, but says he's over it now. I guess I'm just worried that I might go visit for Thanksgiving or Christmas one year and find out that she's invited. Also, I can't help but wonder if his ex has ulterior motives. 

Any insight Reddit????
<bot>: My SO's mother still hangs out with his ex gf after 2 years. Has this ever happened to you?? How did it turn out??