well the Egyptians had brother-sister tandems ruling together for thousands of years. in lion prides, the prides are often led by more than 1 male, who share in the duties of ruling the pride. So Kopa coming back in, makes the pride bigger and requires that more than 1 lion lead it. in short, there's more than 1 king. and by extension, more than 1 queen. so its not a case of kopa gets everything, Kiara gets nothing. Simba and Nala would not permit their daughter getting nothing, shes earned her place in the pride. In short the two of them have to share, and for it to work, they have to get along. and as for the mating thats part of the royal duties, well that where kovu and eventually Vitani will come in. they'll handle that part of the job, for obvious reasons.
