Okay, now, before all of you freak out on me, please consider that this may actually be possible...

Lets look at a picture of both of them...

Do you not see the comparrison? The face expression, for one. It is the exact same thing! Even Mufasa and a few other lions make this face expression in the movie, but I saw no comparison with them. But Zira and Scar are near exact.

Now, you may not think the means anything, but they both have the same noses. How many lions in the movie had black noses? I can only think of four.... Kovu, Scar, Zira, and Nuka. You may think, "Oh, well, that is a lot of lions." But, think about it.... There are DOZENS of lions in that movie. Four are not that many compared to the rest.

Now, I  am not even sure about this next one. But they both have little tufts of hair on their chin. I can't really think of many other lions that have that, besides Nuka.

Look at their ears. They are both pinned back. Now, I know what you are thinking. "Well, they are just pinned back because they are angry." Nope. Of course, it may be possible in this situation. But if you look at pictures of them, they are always pinned back, really. I don't know if any other lions have this feature. I'm just guessing. Females have ears that do pin pack pretty far, though.

Now, look at their colors. Scar's is much darker than Zira's true. But, Zira also has very dark fur, for a female. Almost all females have very light fur.

If Zira were Scar's sister, that would make her Mufasa's sister... So, does that mean she would be in royalty, too? Probably not, because Scar wasn't, until he overthrew everybody and killed Mufasa. It just doesn't seem very likely to me, since she was in a group of outsiders...

So, you decide. Are Zira and Scar siblings?