This has been discussed before, yes. But I dont think it really had its own thread, we just discussed it in an off topic way in various other threads.
but yeah, it tells you in TLK2 that Scar was not the father of Kovu, so who else do you think was? Or is it just someone that we do not know about?
Furthermore, if it is a lion that we do not see in the films, then why do you think he disappeared and left Kovu?