threegether
Together as a group of three.
rare
Our little 6 year old girl is also happy with it, the three of us are having a nice time threegether.
Where it comes from
Blend of three + (to)gether. Perhaps inspired by comedian Victor Borge's "inflationary language" skit. Compare Bislama trigeta (“they three”, collective pronoun).
Adapted from the Wiktionary entry threegether (CC BY-SA 4.0).