I discovered that name of dinosaurs family are based on the largest genus of this family. Example: Tyrannosauridae, Spinosauridae, Ankylosauridae, Triceratopsian,... But is there any family of dinosaurs has the name don't based on the largest genus?

The answer is "Yes". Megalosauridae for example, we don't know exactly the biggest of them, but Torvosaurus is bigger than Megalosaurus. Some of other dinosaurs families have the same case. Also, a family of prehistoric reptile is Pterosaur has the same case. I don't know exactly what did the name of the family based on. But of course, it didn't relate to the name Quetzalcoatlus.