Why go through all that trouble just for a dead stiff? :D
This can only be legal if the man has written expressed consent and desire for this action. Without a written and signed document, this should be denied. It’s stealing, plain and simple. The sperm does not belong to the mother. Hearsay is not permissible as evidence, generally. If he wanted to have children even if he was dead, he should have written this into his will. That’s why they call it a will, after all. The fact that a 21 year old doesn’t have a will is sad, but other 21 year olds can learn from this.
I mean, I would still have issues if it was his wife who was asking for his sperm. The fact that it’s his mother adds a whole other angle of rights to this story – now the mother gets to choose who will create her grandchildren, with no input from the father whatsoever? That just strikes me as being wrong. His genetics are his property, and I don’t believe the mother has any right over the ownership of them at all.