since i cannot double post...i'll just tell you here. memories help form the heart. consumed and infused are two very different things.
memories help form the heart (confirmed in 358/2 days ultimania) and darkness help forms the heartless because darkness act's as it's body.
but unbirths (in my theory) are both darkness and heart fused together as if they were one (not seperated). heartless are just heart's covered in darkness. but unbirths could possibly be hearts fused with darkness.
did you read my thread? i just answered you.