Re (from Candide
"Are humans really supposed to be monogomous, or is monogomy just a construct of religion as a way of supressing the masses? If you see how many people get married, divorced, and remarried multiple times you have to wonder if we are truly made for one-man one-woman relationships."
Given the above train of thought, I'd highly recommend the following book:
"Sex at Dawn: how we mate, why we stray, and what it means for modern relationships," by Christopher Ryan and Cacilda Jethá.
To put it succinctly, everyone doesn't *have*
to be monogamous. Polyamory (and polyfidelity) does happen successfully in numerous people's lives.
I would just do as much reading (posting thoughts and questions along the way) on Polyamory.com as possible. In particular I think a search (and/or tag search) for "polyfidelity" might be in order.
I hope your upcoming visit with the ex and her boyfriend goes well.