counterpartner
n.β Β«Have you chosen a new name for your relationship with each other? My sister calls her former husbandβs current wife her “wife-in-law.”…We often refer to each other as “counterpartners.” A counterpart is someone with whom you share similar responsibilitiesβand we do in regard to the kidsβbut we also regard ourselves as “partners” in taking care of the children. Hence, we are “counterpartners.”Β» ββHereβs one way to introduce your exβs current spouse” by Jann Blackstone-Ford, Sharyl Jupe Mercury News (San Jose, California) June 15, 2005. (source: Double-Tongued Dictionary)