I know they fuck their siblings.
Apparently, lions will exile their male cubs when they become adults in two years.
The exiled lions will either die a virgin in exile or successfully usurp another lion's pride.
Apparently, the ruling lions don't usually last longer than 2 years before being usurped/killed. So opportunities, where their cubs would reach adulthood and make their father interest in them, would be rare.
Am I missing something?