I think you should take a step back. You seem to be taking it too personal. Considering that all sides consented to the actions that took place despite how they had felt. Cuz I could easily say Zero was chasing a woman who was married and had child. And in her loss took advantage of her grief to get together with her cuz he loved her.
haha please be calm! it's totally fine not to like her! i just wanted to tell you that kaname actually gave the two his blessing, right after he tossed his heart into the furnace. it's true that yuki was rather indecisive between zero and kaname - which causes hurt to zero. it's a flaw, i'd say. yuki is a very loveable character, but she's very mary-sue too so i get were you are coming from - but let's stay cool about it :)) all three of them did horrible mistakes, but all are very loveable!
yes they are related! kaname is the founder of the kuran's, hence much older than yuki's parents and the ancestor to all kuran vampires. i'm not sure how far they are, if looking at a family tree since yuki's grandparents were never mentioned(?). but kaname wasn't the father of haruka and yuri, so he's basically her great great great (...) grandfather.
yuki never fully loved kaname since the beginning she was always stuck between zero and kaname so she could never choose between them without one side of her feeling empty and since kaname even told her to be happy with zero she took 70 years to clear her mind and finally be with zero she never forgot ab him nor did she kept stuck to him for the following 1000 years she finally found happiness with zero i think it's a given, given her character development

I'm sorry but the mc yuki is basically slut! That bitch!