affiliate
ally
associate
band together
be in cahoots
bunch
bunch up
cabal
cement a union
centralize
club
club together
come together
confederate
consociate
conspire
couple
federate
gang
gang up
go in partners
go in partnership
hook up with
join forces
join fortunes with
join together
join up with
join with
league
marry
organize
pair
pair off
partner
stand together
stand up with
team up with
team with
throw in with
tie in with
tie up with
unionize
unite with
wed
decentralise
decentralize
deconcentrate
merge
unify
unite
federalized
federalizes
federalizing