I thought I already commented on this...huh I must have not hit submit or something.
I like to believe that Sarafina ventured outside of the pridelands or something. Or maybe came from a different pride to join Mufasa's but may have already been impregnated. Disney likes to try to be at least somewhat realistic, I mean heck all you see is lionesses in the pride which is like the real world. BUT Disney would've made her a father. Therefore he exists, but doesnt exist. He has no name nor does he have a look that we know. That kind of makes it fun though for us fans to create such a character in our minds.
It does bother me though, how many people say its incest. I remember we watched Lion King in high school on one of those lazy days and everyone was talking about it. I find it silly that they thought no one ould notice she has no father...I mean that just leads to people thinking crazy things. That leads to the general population of the world thinking Mufasa was a father and it's incest...i dont know. If I were the producers, I would've done a small scene or something. Like maybe while Sarafina was giving Nala a bath and they decide to go to the "water hole", they go off on their adventure and her father comes up next to Sarafina and they lean on each other like parents do when they're children go off doing things while they're sitting there all proud or whatever. A TINY LITTLE SCENE. Thats all they needed lol