In Flight of the Scions, one of the main characters, Ruben is a little person but the reason for his height was less about genetics and more about the continual influence of many generations being born under the influence of the votim. The Vogal Generation is the term that describes the increased powered, authority, and influence that children of telepaths have on the votim's governance.
In my twenties, I had a friend with osteogenesis imperfecta (OI, also known as brittle bones). He was in my D&D game and we had a lot of fun with our weekly games and getting into chaos. He always created mages with the occasional psychic. When I was writing Flight of the Scions (well, it was called Wind, Bear, and Moon then, he was the bear), he asked if it was possible to have a little person in my world that had awesome magical powers and I thought it sounded like a good idea and took his characters as inspiration.
Fast forward a decade and we aren't interacting anymore. I moved to Iowa and we drifted apart from each other. The problem is that I can't really write OI since I haven't lived with fragile bones or struggling with his massive wheelchair. I can remember bits and parts of what I saw him experiencing and tried to put at least a little in there, mixed in with other ideas that came out of the evolution that resulted in the Isle of Vo.
That is always a fear of mine, that I drifted too far out of my lane to create a character I think is interested or inspired by the folks around me. Maybe I made them too much like a cardboard cutout, or the white savior, or being rescued. The problem is that I will never know, which means all I can do is create as rich of a character as possible and do better when I'm called out on it.
Beyond that, the sterility aspects happens to be a common thread in my stories with powerful individuals throughout the entire world. Some of it ties into the original question of Fedran, “why haven't mages taken over the world?” but other parts are far more personal to me and my struggles. There is partially with the observation that highly successful people have a tendency not to have children; as the United States has progressed, the average number of kids in a family as decreased. It isn't a universal rule, just a general trend.