Isn't it poetic that Zero dies before meeting Ren, in the same way Kaname 'died' before meeting Ai. Of course Kaname returns to meet Ai as an adult(?) vampire (who Zero helped raise) as well as Ren. Not sure whether 1000 year olds would be considered 'children' even in the Vampire Knight universe, despite their child-like appearances (Ren looks like 12, Ai looks like 16??).
**In response to a lot of the comments I've seen in other threads, including the very comment above mine here)**
*table flip* WTF with that ending
This is a bittersweet love story, and therefore quite imperfect. Yuuki loves 2 men, who she demonstrates loyalty and love toward in different ways. Kaname was her brother/ancestor/betrothed, it was hard to distinguish her feelings of admiration (arc 1), obligation (as a sister) and gratitude (saving her for literally her whole life) a part from one another. On the other hand, Zero was her childhood friend who she develops a deep relationship with, but as equals.
"Yuuki is a slut for sleeping with both Kaname and Zero"
I liked someones comment that you can compare it to real life, where a woman can love one man, have his child, then (through no fault of her own), move on to another love and have another child. She does her best to mourn Kaname, then live to the fullest with Zero, before trading her life for Kaname's human one (although I can't help but thinking that Ai is able to awaken Kaname the same way Kaname awoke Yuuki). She definitely never forgot Kaname. But her thirst was also only quenched by Zero. There are ticks in both columns. As for her response that Zero gave her much happiness in their 1000 years together instead of 'I loved him', it's much like this love triangle, complicated.
"OMG incest is bad, shame of them"
Yes incest is bad, in real life. This is a fiction about vampires, even then, he was technically her ancestor (10,000 years removed) who was raised as her brother/betrothed. Her real brother died as a baby.
"Zero was the best character"
I think I saw one comment that described Zero as simply a broody, emo guy after vampire blood, and I agree. I didn't particularly like Kaname more than Zero or vice versa. They were both equal parts likable and unlikable. I kept reading through the nonsense chapters because I wanted to see where the relationships ended up.
Sayori x Aidou
I found it sad but beautiful that they had a human character (Sayori, Yuuki's best friend) choose to retain her humanity and die a regular death. You see Aidou, the vampire father of her children go on living, even expressing a desire to have died alongside her (not yet possible as his research was still incomplete). With Yuuki and Zero becoming long lived vampires, it was a nice contrast to all the violent death (that is really the only way vampires, particularly pure bloods go out).
At any rate, I feel a lot of catharsis having reached the end. How it ended will no doubt haunt me for a few days/weeks, but I like a good story that sticks with me like that.