Happy to have found a place to discuss poly.
I'm 42, married for 19 years, and have been in a relationship with my girlfriend for 8 years (we just celebrated our anniversary). She is my first and only venture into poly (haven't been interested in anyone else). My wife and gf's husband were involved for a time, but things cooled off between them a while back and now they have more of a FWB arrangement. I'm very happy with both my loves, and am committed to them equally.
If there's been any difficulty, it's jealousy (of course). I get along with my girlfriend's husband, but there have been times over the years when his jealousy over the intensity of our (my girlfriend's and my) relationship has created turbulence. Such is life; nothing is ever completely free of static. So far we've managed to work through the issues reasonably well - after 8 years I should HOPE we've gotten adept at it.
Looking forward to jumping into the discussions here!