They were married in YJ, though apparently not legally, since the government failed to recognize him as next of kin (or, in fact, sentient and possessed of rights of any kind). But then he proposed to her in McDuffie's JLA, like they were only ever together.
Two wanks to cover this: either John Smith married her, which became void when the gov't found out John Smith isn't real, or AIs gained legal status at some point between YJ and JLA v4 and he wants to get re-married, but legally this time.