Poly relationship with formerly-mono couple
I recently started a poly partnership with someone who is also with their former monogamous partner of 3 years.
I've been in poly relationships before, in different forms, but haven't entered one that was already in existence (ie: in the past, the initial relationship was created by myself and a partner/partners).
I'm curious if anyone has advice about how to handle coming into someone's life who is working things out with a previously monogamous partner. I can't help but feel like I have a larger hurdle than I'm used to, or like I'm "secondary" in this situation.