So you and an ex are having friendly three-ways with a mutual acquaintance? This is the association you are considering moving to a "next level"?
Originally Posted by UrbanDiplomat
I realize that 3 different, intimately connected personalities will be no walk in the park.
What you are describing here is a triad. There is at least one built in problem with approaching a relationship with the end goal being a triad. There tends to be an assumption of "equal love" which is profoundly unlikely. The individual relationships (A-B, B-C, A-C) will be unique and I suggest going into a triad realizing that reality. No two relationships are alike and while a triad would *seem* to be one relationship, it is in fact three distinct couples.
Either way, don't force a triad. If a triad wants to happen and you are ok with that then let it... but going in with this as the main goal dramatically increases the odds that it will crash and burn.