A preview page from Avatar: The Search. Apparently there is a rumour going around that Ozai might not be Zuko’s father. Now, to my knowledge that has yet to be proven true so it’s still just speculation.
Man on the first picture is Ikem, Ursa’s young love, they were separated when Ozai hand picked Ursa to betrothed. Which is what is happened in the second picture.
But removing Ozai as his father eliminates the beauty of the conflict presented between his paternal line of Fire Lords instigating the war and his maternal line descending from Avatar Roku.
That and he looks like Ozai, too.