I think your trio is made up of two sows and a neutered boar - is that right? If so they need a 2x5 c&c cage.
Moose as a single needs a minimum of a 2x3.
So yes with two joined together 2x6 c&c cages you have the space to split the cage and still provide enough room for everyone.
Moose, while he is single, should be beside your other piggies for interaction between the bars - that is assuming he has come from a reputable rescue and has been through a quarantine period already with them. If he hasn’t then provided he is over four months old, he should be quarantined in a separate room for two weeks before moving beside your others.
You must make sure any cage is his is very secure though (ideally make the cage side two grids high so he can’t climb in with them) as you do not want to risk him trying to get into the cage with the others (it will cause a fight with your other boar and obviously the risk of pregnancy with your sows).
He obviously cannot be with a sow until he is six weeks post neuter so as he isn’t neutered yet then being beside the others is important as otherwise he is going to be a long time without interaction with other piggies)
Do also note that doing so will mean your trio will react to the reduction in space and you may see an increase in dominance (for around two weeks) while they reeestablish their new territories.
