Two years ago I split up with my partner, who was a good man, but always knew he wasn’t the father of my 15-year-old son.

I never did tell him who was, but, give him his due, he brought him up as his own, along with our other two children, and never breathed a word to my son, who adores him.

Our own children were daughters, and he loved spending ‘man’ time with my son. My son totally blames me for the breakdown of my marriage and depriving him of his dad. And yes, it was in a way my fault. I’d found my ex-boyfriend again (he’d gone back to Ireland, not knowing that I was pregnant, and I never told him). But when we accidentally met again, after his return to the UK, the chemistry was instant and brilliant, and I left my husband for him. He’s now moved in with us.

My daughters love him, as I do. I’m in heaven again. Their father has a new partner and is kind but pretty distant with the girls. My wild Irish lover who is charismatic, an artist, a warm and noisy person, is everything their quiet, dependable but conventional father never was.

The problem is that my son hates him. He sees him as a rival, not as a friend. He does everything he can to break us up. My ex doesn’t know that this man is my child’s father, and also hates him. So my son goes round every weekend to be with his ‘dad’ to get away from his real dad, and slags him off.

Should I tell him? He’s so like his real dad that I wonder if they’ll ever get on. I don’t know what to do.

Barbara says: Fifteen is such a delicate age. It’s an age when you’re building your identity, and don’t want anything to rock that process. You kept secrets. No one should ever do that, as they always come back to haunt us. So you need to talk this over with a professional, before even attempting to break into your son’s identity-building process. You need to access counselling. It may take some time.