A question I've always wondered about surrogacy/sperm donors

[Merrydoula]

Please don't be offended by this question, it's just something I had to ask as I've been thinking about it.

When a person uses a sperm donor and has a surrogate or carried the baby themselves, what if later in life when that child grows up he/she ended up having a relationship with their own siblings for example if the sperm donor had other children before/after donating his sperm? I know it's very far fetched and highly unlikely, but what is put in place to stop this happening?

Probably nothing, similar to adoption.

Anonymous sperm donation has ended. You can find out at 18 if you went through a clinic. I believe the clinics also limit how many donations/ children can be conceived for each donor (have heard but not researched this).

Sperm donor from some random on the internet? Nothing to stop this.

Surrogates are not always biologically related to baby..?? Women cannot have as many children as men. Totally different scenario as surrogates tend to either be well-known to the family or live in a different country.

HFEA rules prevent the same sperm donor from "creating" more than 10 families. Once that donor's sperm has resulted in children born to 10 different sets of parents, he can't be a donor any more. Presumably this is to minimise the risk of the situation described in the OP.

Not sure what happens re egg donors/surrogates but presumably the rules are the same.