Understanding Triangulation

I am after some insight ladies, as you do! Going over some of the old stuff.....am in a good place now I know what he is - remember my post The mask Will Crack? So I know what he is and am feeling damn good about getting out of it.

The thing I am now processing is all the triangulation - he did this with me and his ex-wife, almost thrived on it, god there were so many arguments over her, she almost controlled him!! In my opinion, he has never truly let her go, when he was with me the first time, he still carried a photo of her and the kids in his wallet. She got away from him after 10 years of marriage, but she was the one who did it - it seems he has never got over it? And I know now, due to a blip on FB that he is saying to the new supply "I haven't felt like this in 15 years, since I met me ex-wife, that's twice now" - said the same to me also in a different way - told me he had only ever trusted two women in his life, one being his ex-wife and one me!

So what is this all about - why feel the need to triangulate - and why do it continually with his ex-wife??

All very strange. Hoping you guys can help as the jigsaw is finally coming together - just a few pieces left.

Thankyou!