Your guess is as good as mine here, because as far as I know, what the early Deniz clips give us is all the background story there is. If there is more in earlier storylines with Marian, I haven't seen any of it :\ I did get the impression that it's been quite a while since the split, though, maybe six, seven years? Because Marian doesn't seem to have much of a clue about how to handle a teenage kid (granted, his is more to handle than most), which makes me think he wasn't there for most of Deniz's early puberty. Just guesswork on my part, though.