Hi i would like to know if they is any way to merge kinships.
There's no tool for it, if that's what you're asking. We've had a few kinships merge into our, and we've handled the process manually-- invitations/promotions/etc.
Yeah you would have to disband one of the two kinships and invite all members into the remaining kinship. And if you cannot agree on which one to keep then disband both and make a brand new kinship for all members to join.
Something to consider is maintaining a few alts in the prior kin for storage. I know our kin recently expanded into a 2nd kinhouse and it's done wonders for our ability to keep consumables stocked as well as necessities like CD uru items, and just general fun stuff (fireworks!)