If the sperm donor gave his sperm to be used by others, why would he want these children now?
Thanks for the info. I was imagining them half Chinese or Japanese, now I understand they are half Indian or Pakistani.
I don't think it was a donor -- almost certainly another man whose wife/partner was a patient at the same clinic, and the samples accidentally got switched. And if that man's wife/partner wasn't successful in her attempt to have a baby, that would be plenty of motive for the man to try to get at least some contact with these twins.