Anyway, I feel like it's going to be difficult to learn how Brian passed away because it seemed like something tragic have happened based on Sol said that he was not able to protect him and regretted it so much.
No he's not an extension of Brian's personality
That's just what I think. Technically he's like what Brian would be when in toxic environment. I don't know about other people, but when I read most of the chapters, it make sense to me Brian and Ian is in fact the same person. The soul is the same. Personality similar. Values that they hold similar. Ian is more aggressive (far more agressive than Brian was from earlier chapters) because of his traumatizing childhood experiences. Eventually, there will come a time where the memories will merge and Ian will remember all the past memories. This has been mentioned by the mother dragon earlier in the chapters. You can't separate Ian and Brian because they're the same person, born at different time. Lorkan or whoever Cardinal Brixton is could never compete with this, even with imprinting. They're soulmates.
No matter how many times Brian would be reborn, he will always find his way back to Soleite.
Please, I read up until chapt 50 and when he tries to avoid communication by suggesting I chuckled . Kind of understand why Sol loves Brian very much. And I also understand why Ian is the way he is. He started his rebirth with toxic environment, wrong people,wrong obsession. I bet if he rebirthed in Archaia he would be very much like Brian. That being said, I feel like Ian is just an extension of Brian's personality.