Child maintenance other children

[Neweternal]

I have a son now 11. Sons father left as soon as the line turned blue never to be seen again. I received through attachment of earning from CMS maintenance. Today I received a letter saying the amount I'm getting will be reduced as his father is now living with someone who receives child benefit. So does that mean my son has a brother/sister or is this just a live in girlfriend child? Would the CMS tell me if I asked? Would I have to go to the registers of birth and ask? They stay less than a mile away and I don't know what to tell me son if truth be told. I'm not overly interested but I would appreciate knowing if he has another biological child.

It’s not your business to pass on this information. I say this as someone who thought they only had one younger sibling but found out last year that I have another one who was adopted. My mum had always known but my dad (the baby was his) was the one to finally fess up.

Yes it is my business. I don't care about step child status, if it had been a biological child I would have obtained a copy of the birth certificate (public record available online). You know it affects matters in death too, here in Scotland you have legal rights and children cannot be disinherited. Also if my son is under 18 the rights of the estate are quite different too. It affects the amount left. Anyway doesn't matter as I said CMS confirmed it's a step child, which I agree is none of my business, unlike biological!