Zira and Sarabi are sisters in my mind. Their father is a dark, "pridelander-shaped" lion, and their mother is a pale "outlander-shaped" lioness. Sarabi is more of a daddy's girl, and Zira favors her mother.
Zira had a small crush on Taka before it was announced Sarabi was betrothed to Mufasa. She got over her little crush, and accepted Taka as a brother-in-law. They remained good friends, and Zira supported the idea of lions and hyenas being together. Vitani and Nuka was the outcome of a night with a rogue male. Scar had Kovu with a lone lioness, and after the death of the two, Zira was left to raise him.
There's my little theory thingy.

i love the idea that sarabi and zira are sisters !
nicely done !