A fascinating concept that it would create a fundamental shift in societal assumptions such that an individual would be seen as more dangerous than a pair. I look forward to reading the finished novel.

"her Alt" or just "his Other". Co-minder as an official version? Government Paired Truce Guarantor becoming "my Geep" (soft g) There are lot's of possibilities but I agree with Troy, for gereral usage you would need a slang version as well as the official one.