There is no such thing as ethics for cats. It is natural for cats to be in heat and mate. There is no need to use human standards to view this matter. If you really can't accept it, just neuter the male cat and abort the female cat's babies.
In fact, in breeding work, backcrossing is often used to enhance the performance of a parent's traits in hybrid individuals. The offspring produced by the backcross method are called backcross hybrids. The parents used for backcrossing are called recurrent parents, and the parents not used for backcrossing are called non-recurrent parents.
