No. She would have to be Mufasa's sister but the only place where that has been mentioned is Disney's official web site which is RIDDLED with ridiculously obvious information mistakes when it comes to the Lion King movies. Such as a claim that Nala does not appear in Lion King 1½ when she most obviously does. And many other similar false informations.

Hence, that web site is hosted by people who had nothing to do with the films and who apparently dont' even try to keep their facts straight.

No. Zira has no biological relation to Simba what-so-ever, as far as the canon facts go.

Unless Scar married her. Simba would have a evil aunt.

thats right. scar should have married her to become Simba's aunt but there's no evidence for that nor for having any blood relation to him.

Well Zira was Scars mate so I believe she was he's aunt

Zira is not Scar's mate at all, she was more likely his follower. Zira is more like Simba's age as well since they have young children.

Yes, because Zira mated with Scar, in a deleted scene she says, “And I Zira, his devoted queen.” She was ranting about how things used to be after Kiara’s birth. Another theory might be is that she is Sarabi’s sister, because she does look a lot like her. This would make Zira Simba’s aunt since Sarabi is Simba’s mother. Either way, Zira would be Simba’s aunt.