Who do you find more attractive? Michi or Ursa? Have you ever cheated on Ursa while you were still married to her? I know Ursa probably cheated on you emotionally!
I was raised to be a perfect prince and never go against the honor of the royal family, so no, I never broke the honor of my marriage or pursued any woman other than my lawful wife. I wish I could say the same about said wife, who has lost all decorum and doesn't hesitate to rub her affair with the stinking peasant in society's face, even though we are still married. And we will remain married. Forever, as our marriage vows demand. Zuko may have legalized divorce to get revenge on me, but that will never happen. Ikea the Stinking Peasant is going to have to come and kill me if he wants to be rid of me. If he has finally found a sword that isn't made of wood.
You see, I deeply detest hypocrisy. When I was young, I had to endure Iroh chasing after all the maids even though he was fully aware it wasn't honorable. I'm not like Iroh. A maid's job is to clean up (and occasionally dodge Azula's fireballs), not waste time on amorous dalliances. A Fire Nation prince should be focused solely on winning the war.
However, you mentioned Michi. My destiny was always to marry Ursa, but in another world, things might have been different. I was truly tempted to court her in my youth; no one can deny that she would have made a perfect wife.
And yes, she always had that same unusual, sharp beauty. Her daughter bears a striking resemblance to her. Zuko must be completely out of his mind (more than I suspected) to allow Michi's daughter to leave him.