I have a Westeroes Headcannon. So we all know that sheepstealer was the most successful regarding the wild dragons. This means that greyghost and the cannibal can choose a rider but haven't gotten the right person. I can see Cannibal only having a one dragon rider and choose not to have another after.
I see Cannibal as the wild dragon that you need to have a special bond with because he saw something in the character for him to choose them as the rider. When his rider passes away, whether it be of old age, during childbirth (if they are woman) or even assassinated). I can see him rejecting anyone.
Even if the character had kids of their own. The kids would accept and understand that the cannibal will always be their parent's dragon even in death.
