Looking for book recommendations for my KD’s child…

My spouse and I are going to be starting IUI soon, and my brother in law is our gamete donor. He and his wife have a one year old son, and plans to grow their family. We would like to supply them with children’s books on the subject of donor conception, but through the point of view of their child(ren). Basically something that expresses having a cousin who is a cousin but also a half sibling. Are there any published children’s books out there like this? Or will we probably end up making our own?