Well a person born via artifical insemination should be careful to avoid dating someone else conceived in the same manner. Besides, in many adoptions, even the mother isn't really sure who the father is. Even with a donor creating 20-30 children, it is unlikely out of the large number of babies born each year you will marry your brother or sister by accident outside of a soap opera.
Certainly if I knew I was conceived by AI, I would avoid dating a person conceived the same way. But why would you think they would know? It seems to me that would be something the parents would be unlikely to reveal to their unnaturally-conceived children.