There is a world somewhere between reality and fiction. Although ignored by many, it is very real and so are those living in it. This forum is about the natural world. Here, wild animals will be heard and respected. The forum offers a glimpse into an unknown world as well as a room with a view on the present and the future. Anyone able to speak on behalf of those living in the emerald forest and the deep blue sea is invited to join.
I think males instinctively seek out the company of lionesses when they leave their pride. So having the company of their sister means they're not as 'motivated' to spend time with other lionesses.
In that clip we saw of K4 telling K5 to stay away from the Nkuhuma lioness, usually the less dominant brother would just wait his turn to mate. But in this case he went off and found the other brothers. I don't think he would have done that if the sister wasn't around. Just a hypothesis.