I have Bobby who is FeLV negative, FIV positive.

Cats with FIV can live a full life, and can mix with your other cats IF he cats get along and do not fight. FIV can be passed by saliva. My cats do not fight, they all get along fine.

Cats with FeLV have something which is much more contagious and in general, they live only with other cats who have feline leukemia. SO they can't contaminate each other.

Did you have specific questions? What are they? Do you have a cat with one or both?