Biologically he's the father. He didn't know for sure that donating his sperm would not implicate him in the future lives of his children, given that he should have found out his legal obligations to the children prior to agreeing to donate.
That being said I think the women who brought the children up should be financially obligated as well as the biological father.
As a tax payer I'm fucked off with being a surrogate dad to thousands of children from failed relationships. I have no problem with parents paying for the well being of their children, even if they can't be bothered.
Do not donate sperm if it bothers you that one day your biological offspring may come knocking!
That being said I think the women who brought the children up should be financially obligated as well as the biological father.
As a tax payer I'm fucked off with being a surrogate dad to thousands of children from failed relationships. I have no problem with parents paying for the well being of their children, even if they can't be bothered.
Do not donate sperm if it bothers you that one day your biological offspring may come knocking!