By main "mom" I'm refering to the person you end up with if you dont got down the harem route. I could be misremembering, but if you chose like 1 person, dont you adopt V with whoever you chose in the end? In my playthrough of AR1, I remained faithful to the first love (cant remember her name for the life of me).
But in 2 its revealed that you ended up with the Fujikawa girl.