I don't think it's a big deal. Like so what if they're friends? Unless your ex is still seeing you or unless you have some unresolved feelings for your ex it really shouldn't be a big deal.
I'd be really pissed. Get ready for ex-wife #2, because them ganging up on you is never a good thing. Either one or both sought each other out in order to cause drama. Ruuun.
Well I think we know who they're going to be talking about..
Damn.