Where are all the other male lions ?

What species do you think Scar was?

I don't know how you forgot about Scar but other then Scar, Simba and Mufasa there really wasn't any other male lions

In the real world, a pride of lions is usually headed by 1 or 2 male lions. And these 2 are either brothers or very close friends. The male lion(s) fathers all the cubs in the pride.

So technically, Nala is either Mufasa's or Scar's daughter.

"I'm the dude, playing a dude that's disguised as another dude".

Nala's parents, and I imagine other lions, are probably either killed in the stampede or intimidated in to moving by Scar who would feel threatened by another man of his kind. The lack of male lions is one of the main reasons why Scar is able to keep such tight control over the rock, and the insecurity is demonstrated when Simba approaches Scar with murder in his eyes. Nala's mother and father would not voluntarily leave without her, and must be part of the original group of residents since their daughter is betrothed to Simba as soon as she is born. We know that Nala's father is married to Sarafina, who is friends with Sarabi, and can obviously not be related to Simba anyway given the arranged marital plans. He exists but is not shown.