MIGHT CONTAIN SPOILERS! I ALSO GOT QUESTIONS

Okay, this is a very long reply, LOL. But I think a lot of people are curious too, so here goes, I'll do my best for you!

AoAo's soul was previously... Aoao (or Ao Yue, his original dragon name when he was born into the royal dragon family), and AFAIK, he's had his soul broken and repaired--and I'm pretty sure he's even in the same body, just regrown from babyhood after his soul injury. Not totally sure on that, though. He may have literally been reborn in some magical way, but I'm reasonably certain he wasn't actually reborn through childbirth. Ryan/little black dragon has Jifeng's soul, and as of yet, it hasn't been shown how that happened.

In their past, Xuan Yue (AoAo/Ao Yue) cursed Jifeng (who later shows up inside Ryan) to eternal loneliness and heartbreak, and I'm assuming that's why they are stuck in this cycle, though I think Xuan Yue intended to die with his own soul pulverized and never come back. He used his soul and Jifeng's blood to begin the curse. Xuan Yue wasn't counting on his big brother, though--and Ao Gu saved Xuan Yue and had Dr. Sun (I think) help him put the shattered soul back together with a soul needle, and rebirthed as AoAo. AoAo doesn't remember anything for a loooong time, but his memories are starting to come back. AoAo was reborn without a 'heart', the ability to love and feel romantic desire, because it would be too traumatic for his shattered and repaired soul to go through another heartbreak.

Ao Gu and Xuan Yue are actual brothers. When Xuan Yue/Ao Yue was an infant, his father sealed a demon inside of him. Presumably, the dragons meant to destroy the demon once it was contained, and I think Ao Yue had a strong body capable of holding the demon inside for a while--long enough to kill it, anyway. I wont say how Ao Yue survived because that hasn't been translated yet, but it's obvious that somebody rescued the baby demon container and stole him away from the Dragon Palace before he could be killed (or whatever else the dragon higher-ups had planned for him). So, Ao Yue was taken away from the dragon palace and given a new identity as Xuan Yue. Ao Gu remembers him, but Xuan Yue doesn't seem to recognize his older brother. I guess he was too young when they were separated.

Jifeng's story is shown soon, in some upcoming chapters, so I won't spoil that, but a lot of their backsoty was shown in that school drama production. Jifeng, supposedly a cultivator/demon slayer (but it's suspicious) went to the mountain to slay the demon/dragon/whatever unholy creature Xuan Yue has become. Instead, it looks like he fell in love with him instead. Only part of their history has been shown so far, but the flashbacks indicate that at one point Xuan Yue gives his pearl to Jifeng voluntarily, though it's hard to tell. And yes, it appears Jifeng develops an obsession with Xuan Yue, locks him up, and torments him in various horrible ways until Xuan Yue can't take it anymore and curses him.

I think the Eastern Dragon King was responsible for the demon and was barely able to keep it under control with barriers and such. They needed a strong body to contain the demon (so they could then destroy it, I think, but I'm not sure about the 'destroy' part. Either way, things looked bleak for Ao Yue/Xuan Yue/the 2nd dragon prince/eventually-AoAo). I don't know if the first prince, Ao Gu, was passed over because he's the heir or because he didn't have the right kind of body to contain the demon, but Ao Yue was definitely strong enough, and I suspect he was actually conceived and born with that very purpose in mind. I think King Dragon Dad didn't necessarily want to do it, but he had to do it, and it sucks for everyone involved, especially Ao Yue. King Dragon Dad also holds resentment toward Ao Yue because Ao Yue's mom/Dragon King's queen, died in childbirth. Dragons don't seem to get over losing a lover very well. I think the king feels bad about it tho.

Anyway, that's a lot, and some of these things haven't been completely explained in the comic yet, so we can't be 100% sure about all of it.
Hope this helps! ヾ(❀╹◡╹)ﾉ~

Thank you whoever you are! I hope you safe days and travels.

You're welcome! Have a lovely day and stay safe too (=・ω・=)

Omg your explanation is sooo wide and I had forgotten some point you said. I had a question, where it said that ao yue was kidnapped or stolen before they could kill him?? From what I understand, maybe they just expected he wouldn't get to live so much. I also be looking forward now that their flashback is being explained :-)

It's shown in chapter 31, during the school play production. After baby Ao Yue has the demon sealed in him, a single panel shows a mysterious cloaked person picking him up and carrying him away. The person says, "poor child, I'll take you away from this place". Later, we see him with the name Xuan Yue, and he has no memory of what happened to him, his life at the palace, or his big brother. Which is pretty natural, I guess, since he was only a toddler when it all happened and he's been living away from the palace for most of his life. At chapter 96, a series of flashback chapters begins, in which we start to learn about their history, and we find out who that mysterious cloaked figure was.

I'm not certain the dragon clan was going to kill Ao Yue after the demon was sealed within him, but some things other characters say and do imply that may have been the case. It seemed like it was impossible for them to destroy the demon while it was unsealed. A lot of this stuff is only hinted or implied in the earlier chapters, but once the flashback starts, a lot of it is clarified. Don't worry, it will all be explained, and the flashback is really long and detailed (and still ongoing, if that's not too much of a spoiler!) and it looks like everything will be revealed at last. ヾ(☆▽☆)