I heard somewhere that in the UK there is a maximum legal number of 66 monkeys that any one person can keep as a pet. It seemed like an arbitrary number to me so I wanted to ask if there is a maximum limit to the quantity of a certain types of animal an individual can keep as a pet e.g. monkeys
Ask your Local Authority Having Jurisdiction.
You may not be able to keep monkeys at all; animals classified as wildlife require special permits in many countries.
There may also be local ordinances. I believe people can't keep roosters my town for noise reasons, though they can keep hens.
There may also be laws intended to prevent "animal hoarding" cases. And you may need to be able to demonstrate that the animals are getting suitable care.