Either that, or Zarkon just refuses to admit that Cossack is his son.

Check out this shot from the last DVD set's deleted scenes. Cossack does really look like he could be Lotor's dad or older brother here...

Yeah, Z has this weird fetish for snogging in toad ponds

That lost ep was full of confused (read: lazy) char designs. I love Hagar's look in this screenshot you posted. It's almost like she's thinking the same thing ("Aw man, not ANOTHER one").

I like the regular pupiless Cossack, though

It is freaky seeing Cossack with pupils, that's for sure. I like him better without them too.

I do wonder what the dialogue from this scene would have been... as it plays out, Zarkon seems to be hollering at them all, then Haggar leans down over Cossack with this malicious look and next thing you know, Zarkon's waving his scepter right at Cossack and he's in oh-shit mode. I guess the blame rolled downhill and he was the sucker at the bottom that time!

Oh PLEASE change his eyes back before mine start bleeding

It is quite possible for Lotor not to be Zarkon's son, but rather he being born of the species that seems to make up the majority of Zarkon's empire (Drule) it would make sense politically for Zarkon to "adopt" Lotor (perhaps from influence of Lotor's mother), as a gesture of goodwill towards the Drule.

Or if Cossack is Lotor's father, it could also be a situation where politically Zarkon would take Cossack's son and train him as a Prince.

This would give one reason to justify Lotor's desire to see Zarkon dead. Despite being powerhungry as well, he could have been the key member of a political coup/revolution to overthrow the cruel Zarkon and save his people.

Ironically, this would also explain certain changes in mood and temperment esp regarding the Princess Allura, as she symbolises freedom from oppression.

Do I think Lotor can turn over a new leaf and be good, no not really, not totally good... but I do think that he wants freedom. He knows he has to bide his time however, as he is in a very dangerous political game in which flippant comments are taken seriously and who is to say how many other "Lotor"'s came before him?

However if Lotor did succeed in overthrowing Zarkon, if he did become the King of the Drule, I wonder if he would try to take the steps needed towards peace. It's possible that he would not, and just carry on the warlike culture of his people for the sake of keeping his people happy.

I'm not really sure how Drule society works, but from what I've seen they enjoy warfare, and acts of aggression towards planets/races/cultures they deem weaker than themselves. Even in recreation they are like the Romans with their gladatorial areas where the slaves from these planets are forced to fight or die. It's a culture mixed with pride but lacking honor. They would fight dirty if they had to, in order to attain their goals.

Although humans have also been prone to fight and behave as such. We only have ourselves to look at for models when building a story about an alien empire, therefore the fight between the Voltron force and the Drule can be speculated as symbolic of the fight between the absolute evil in mankind against all that is good about mankind.

This of course flows with the Buddhist concept of internal struggle and destiny. Is Lotor in control of his destiny, does he have the strength to challenge the authority for what is right, or is he just going to replace that said authority with another which is just as bad?
If Lotor could change, would he or are the forces of his destiny so strong that he cannot change. (A tiger cannot change it's stripes)

Nevertheless, he is an interesting character to observe. Perhaps the writers of the second season were trying to show that Lotor was not just a two dimensional boring figure, but actually had more depth to his character than what was seen in the first season.

That was one thing I liked about Lotor's character. He had the option of taking different directions. In retrospective, Lotor's character could wind up the same way Hazar's character was in the Vehicle Voltron series. They're wanting peace or luv one minute & power the next minute.

It's no wonder different writers have paired them up in many fanfics, especially having them both attend the Drule Academy together.

It's a wonder as to whether or not Hazar did attend the Academy. Lotor mentioned he attended when he was speaking to Mogor in #37; Lotor's New Hitman. I can't wait until the Vehicle episodes come out, so I can explore Hazar's character more. He was my favorite character from VV series.