Knock yourself up was the first SMC book I read. Really got me thinking. There's a tiny clinic with willing to be known donor semen but everything there seems to be 10+ years old. So the donors will be older now and not necessarily in the same place in his life being available to be available. I was going to go with the willing to be known donor until I learned of the time lag. Part of my reason for wanting known though is previous children with their father.