They have a unique process for this, the alpha male will select a male kitten of his blood line and raise him up for this once the alpha reaches his last years. He will be more protective the kitten than mama would be. The male kitten will stay with him until the older dies and at that time he will take over the role.
The alpha kitten is usually the largest and strongest of the litters and will grow much larger than his parents. It is similar process that wild cats do.It is truly unique and not commonly thought of that domestic cats will do or have.