A/N: Here is me, turning my hand to multi-chapter fics.

Thank Yous: A few are in order here. One to lilsteves who offered immeasurable help in Chapter III; another to scnaggie who somewhat inspired me in Chapter IX; and a huge glomping thank you to all of you wonderful people who have reviewed. I will create enough Horcruxes so that you can all have a little piece of my soul. You know you own it anyway.

Warnings: Slash ... duh. And, as this is set during OotP, i guess, at 15, Harry is underage. If this doesn't sound simply irresistable to you slowly back away.

Because Sirius and Harry don't understand what this is between them, because it's inevitable and necessary, but mostly because Sirius isn't always sorry for falling for his best friend's son.

I Wish I Was Sorry – Chapter I

I wonder what you would say if you knew what I was doing right now. Would you scream at me? You'd probably hit me. Maybe you'd hit me again.

God, who am I kidding? You'd beat the living shit out of me. You were my best friend I know exactly how you'd react. I can picture the way your face would contort with rage, the way your eyes would burn with hate. And what about Lily? If she knew she'd probably cry.

You'd both think me a monster; surely I can't be the boy you adopted as a brother, the man who stood beside you on your wedding day. The friend you made godfather to your first and only child.

Because right now, I'm fucking Harry. Harry. Your son.

And God, I wish I could say I'm sorry. I wish I could sincerely repent this. I wish I could say this was a stupid mistake, something that shouldn't have happened, preferably as a result of copious amounts of alcohol. Fuck, I'd even go with this is the first time and it'll never happen again.

But the thing is, I don't regret this and I've been stone-cold sober every time this has happened and this sure as hell isn't the first time, and I hope to God it won't be the last. And perhaps the worst thing, the thing that makes this whole tragic mess unforgivable, is that I'm not sorry.

But maybe I should explain myself a little better; maybe I should tell you the whole story. I don't want you to think I'm a sick pervert that's just using your son for a quick fuck. No, it's nothing like that.

So, the beginning. I guess it all started in June, after the disastrous and horrific Triwizard Tournament, the night Voldemort came back to power. Dumbledore immediately reinstated the Order of the Phoenix and I was quick to offer him number twelve, Grimmauld Place as headquarters. You know how much I hated that house, James, and I thought I'd seen the back of it at sixteen.

Then in early August Harry left those wretched Muggles and came to stay at Headquarters. Everyone says he looks like you and I wonder he doesn't tire of hearing he has his mother's eyes. I can't dispute that, he does, it really is quite astonishing; sometimes I'll be speaking to him and could swear it's you talking back. But somehow he is completely different to you, he is entirely himself.

Little things that perhaps I shouldn't notice: like the way his eyes half-close in lazy contentment when he sits quietly at the kitchen table listening to everyone talking around him; like the way a slight frown on concentration creases his forehead when he reads the Daily Prophet; like the way he smiles softly when he looks up and catches me watching him from across the room; like the way he gasps my name when I kiss the hollow of his throat; like the way he bites his bottom lip when my hand slips between his thighs.

At first I tried to convince myself that I was worried about him. He was different when he came back from the graveyard. Haunted, disturbed even. And who could blame him for being like that? Seeing that Diggory kid die and witnessing Voldemort's return, it would be enough to send any grown wizard mad. But my God, he's brave. He manages to take most of it in his stride, only occasionally lapses into a desperate panic. You'd be proud of him.

So I told myself that I was keeping a fatherly eye on him, that I wanted to protect him and what I was feeling was natural, like how a parent feels. But when I caught myself staring at him and imagining pinning him to the kitchen table, bruising his lips with kisses, pushing my hands beneath his clothes, making him beg for more, fucking him senseless, I knew I was screwed.

I tried to distance myself from him. I tried to stop it from happening, James, I really did. But I guess that isn't much consolation given that I caved in anyway. I would hide out in Buckbeak's room, hoping everyone would presume I was in one of my infamous moods, a Black family trait, hoping I could be left alone. But he would always find me.

He'd quietly slip into the room and sit beside me on the floor, our backs against the wall. Sometimes we would talk, mostly about you, and sometimes we would sit in silence, there being too many things that needed to be said. Sometimes he curled up beside me and rested his head on my lap and I would gently stroke my fingers through his hair. I don't think he knew what was going on between us – hell, I don't think even I did – all we knew was that we simply had to be close to each other. It felt natural and necessary and inevitable. It felt like drowning.