They can't clone themselves…..
Much like a RH- monther and a RH+ father have difficulty having a child….
IMO, they have to inbreed to continue the bloodline. Also why they have to do own the genetic testing labs/records.
Q would likely take out all these types of places and databases.
If you destroy their knowledge and tracking of the bloodline…… you've killed their ability to continue to grow.
Lock up and/or Kill the rest……
Boom. You have to rid/contain the earth of the bloodline I suppose.