Please help - I'm trying to sort out a 2 Apple ID mess.

I have for the longest time had two Apple IDs, one of which I've used for my iPhones.

But for the new phone I'm about to buy I would like to use the other ID and, if possible, merge it with the one I've used previously for my phones.

Is this possible?

I'm thinking in particular of my SMS/iMessages, Contacts and a shared photo stream I set up on that account.

Thank you kindly in advance
Philip