I probably knew that at some point, I'd have to have a conversation with my biological son, Peter, to tell him the truth.

But I wasn't happy that it had to be this way.

Peter was surprised to get a call from me. He has always called me Uncle Andy and thought I was just a good friend of his parents.

I invited him to a quiet pub to have a drink. He was eighteen, I was forty.

He came in and I bought him a pint.

"Peter, I have something to tell you," I said. "You might not like it."

He looked perplexed and told me to go on.

"Well, I'm sure you've noticed that there are similarities between us. We're both 6ft 3ins and you look quite a lot like me."

"Yes."

"You were taller than your dad, Colin, when you were fourteen."

"I know. What's your point?" I could see in his face that the truth was dawning.

"The point is, Peter. That I am your biological father, although Colin has his name on your birth certificate, brought you up, and has far more right to call himself your dad than I do."

Peter looked stunned, a bit lost for words.

"You really had no idea?"

He stuttered a no.

"You look nothing like Colin," I said. "It's something called 'Handsome Son Syndrome'. You're way better looking than Colin. You are the result of your mother having sex with a physically superior man to her husband."

"So you had an affair with my mum?"

"Sort of. Would you like me to be totally honest?" I replied. "You might not like what I have to tell you."

He nodded.

"I've been your mother's lover since she first met your dad," I told him.

I told him that when Colin brought Diane, his new girlfriend, out for the first time when we were students, I was impressed. She was stunning. A great body. Colin was short, a bit chubby and she was way out of his league.

But he was clever and witty and always good company.

As I was sober that night and Colin wasn't, I offered to drive Diane home. She was nineteen and wasn't at all experienced and was a bit nervous. But she invited me in and I fucked her. In fact, I took her virginity.

I told her I didn't want a relationship with her and that she should stay with Colin. But we ended up having sex together at every opportunity.

"You bastard," said Peter.

"Well, it must be hard to get your head around it. But it's saved their marriage because I satisfied your mother in a way he never could," I replied.

"What do you mean?"

I told him that Colin provided her with everything she needed. Financial security and a good home and he was a great dad. They really were best friends. He is a good companion.

But Colin wasn't sexually attractive. I wiggled my little finger at him.

"And, you know, he is not very well endowed. He just didn't do it for Diane in bed. So I gave her her orgasms and, well, her children."

"You mean Claire and Sam are yours too?"

I nodded.

"And my dad, er, Colin, doesn't know that?"

I chuckled. "Colin is well aware of the situation," I told him.

Diane and I had a mainly sexual relationship. When Peter was younger and didn't understand, I often shared the master bedroom with her, while Colin slept in the spare room.

It was an arrangement that suited us all. Diane and I had great sex. Colin didn't have to "perform" and try to do something he would never be very good at.

When Peter got older, we had to be more careful. But we still fucked a lot.

"So when did this end?" Peter asked.

"It hasn't," I replied slowly. "In fact, I fucked her this morning. We met up to discuss you, and we ended up in bed again."

Peter was shocked.

"I cannot believe you," he said. "Do you have no morals?"

I let the question slide and he asked what we needed to discuss.

"Well, it's Oona," I replied.

"My girlfriend?"

"Yes. Er, this is difficult. But as soon as I saw your Facebook photos, I knew I had to talk to you."

He looked surprised.

"What do you mean?"

"Well, I'm afraid that this won't be easy to hear. You see, Oona is my biological daughter."

The colour drained from his face.

"I don't believe you!"

I let the information sink in.

"Oona's dad is Chris, not you," he said.

"Chris does think he's her father, that's true."

Peter was dumbfounded. The pub was very quiet.

He whispered: "You're telling me that I've been fucking my own sister?"

I nodded.

"We had never planned to tell you that I was your biological father, although I thought you might figure it out. But Diane and I met today and decided you had to know. Only Philippa, Diane, and I know about Oona."

Philippa had died three years earlier.

"You got Philippa pregnant too? At the same time as you got my mum pregnant with me? How could you? How many other half-siblings do I have?"

I laughed. "Sorry, Peter, but do you really want to know?"

He said yes.

"At least sixteen," I replied. "You're the oldest."

He was shellshocked.

"Peter, when you look like us, we get a lot of offers from women," I said. "I'm big down below and I enjoy fucking - and I think that I should father children. It's what we're programmed by nature to do."

He was open-mouthed.

"I have a rule though. I don't want to get into a full relationship with all the responsibilities that that brings. So I fuck only married women.

"If they get pregnant, they can tell their husbands it's his. I've had to only have sex with white women because of that.

"And, over the years, quite a lot of the husbands have known about me and have accepted me servicing their wives, just like Colin does. They call men like me bulls and men like them cuckolds."

He said, "They just accept it? Why?"

"Because they know they don't satisfy their wives and they know their wives deserve satisfaction. Some husbands like to watch. Others know about it and turn a blind eye. Colin soon accepted the situation."

"They watch and don't join in?"

"They just aren't involved in the sex itself, although some wank while they watch. But some lick out their wives after I've cum in them. A few clean my cock with their tongues afterward."

Peter sighed. He had a realisation.

"You love your life, don't you? You're always really happy," he said.

I smiled.

"Yes. I was at my happiest when I found out that Diane and Phillipa were expecting my children at the same time," I said. "I'd got my two best friends' wives pregnant and they were going to have kids with far better genes as a result. I'd given my friends something priceless."

"You honestly think you're helping these men and women and creating a better world?"

I smiled and nodded and said, "Yes, without a doubt.

"It's what animals do. The alpha male fathers the offspring. It's nature. Farmers do it too. They choose the best male to father calves and lambs, for example."

"So what are you going to do about Oona?" I asked, changing the subject.

"I don't know," he said. "I suppose I really should call it off. But I love her. What do I tell her?"

"The truth will be difficult," I replied. "It would turn her world - and her father's - well, Chris's - upside down."

Peter was stuck for words.

"I could just tell her I wanted it to end," he eventually said. "But she can spot a lie from a mile off."

I looked at him and felt so sorry. He didn't deserve to be in this position. To be fair, it never crossed my mind that it might happen.

"I could just carry on with her and adopt your morals," he sneered.

"I really don't think that would be a good idea," I replied. "She is your sister."

He looked lost and afraid.

"You could fuck someone else and admit cheating," I suggested. "That would mean she'd end the relationship."

"Is that your answer to everything? Fuck?"

"Maybe!"

"You would like me to be like you? Fuck married women? Spread my genes?"

"I don't have a right to tell you how to live your life. Colin is your dad in every sense but one. He has brought you up well, given you your values and morality."

With that, he knew what Colin's advice would be. He accepted that he had to break it off with her.

I was so relieved.

He sat quietly for a minute or so.

"Do you think I'd be as happy as you if I did what you do?" he asked me.

I smiled. "I'm sure you would. And I'd love to become a grandad when you spread our genes."

More to come