Responses
Alek called Hen and told him a lie so they could meet while Ivan found out that Hyun mark was Alek's (because the studies reveal that the pheromones in the mark weren't compatible with Ivan's I think, in this I'm not sure because the spoilers weren't too specific), after that it looks like Alek released pheromones and this affected Hyun so he entered in heat. There's no more after that because the manhwa haven't been actualized but I hope this helps you

I'm not feeling sorry for Alek, Hen liked him and he didn't give a fvck about him but now that he's in love with Ivan, he like him, brave of him because now he want to separate them when they're being finally happy
SPOILER (to be on context with my comment)!!!: Hyun's mark it's Alek's, not Ivan's, Hyun enters in heat and Alek take advantage of it so he can take care of him while Ivan is heartbroken because he can't do anything after Alek told him that he's the only one who can help Hyun.