MFC doesnt have joint accounts so just keep both open to be both verified on MFC and you're fine.
SM has separate couples accounts and you need to apply for a new one to get that. You cant merge accounts or anything, it has to be brand new. Depending on if you wanna keep your followers and such it may just be better to keep camming on one of yours.
CB same deal as SM. Cant merge accounts so you need to get a new one and decide if that's worth it or not for you and your situation.