(Just a thought, maybe all these speculation posts about Uru, Ahadi etc. belong in "Beyond the Lion King", since they're not canon to the first movie (or any of the movies? Just saying)
Nah, I'd say the most popular theory is that they are both of the same father - people speculate about where characters' fur colours come form all the time but most of those theories can be debunked if you consider that Mufasa and Simba are the same colour yet Sarabi's fur is significantly darker...
This was actually the first time I'd ever heard of this theory tbh