Board Thread:Manga/@comment-39898841-20190622181312/@comment-38964308-20200615002528

Jumbernaut wrote:   Yeah, it's a bit convenient for the author to solve this problem with one line, "they are all dead", but considering how convoluted this is, to me it's good enough.

But I'm satisfied now with the hypothesis that the "Royal Bloodline" is determined by your original family name, kinda like Jon Snow, born Aegon Targaryen. What matters is the "birth certificate", or for Ymir, she looks back into your memories and sees what your mother called you when you were born.

The only problem now are the other descendents from Karl Fritz inside the walls, Uri's Reiss uncles, etc. I can imagine that, since they knew being part of the royal bloodline meant you could one day have to become a titan, eat your relative, inherit his memories, be bound by the will of the "First" King, and only live for another 13 years. So, it's not unreasonable to think many of the siblings would choose to adopt a different name, from their spouse, and live their own lives separate from this "royal curse". This could explain why there are no other "official" royal descendents inside the walls. I understand your point,however, if they were really some alive relatives,they would have been chosen to inherit the founding by Rod Reiss instead of Historia, maybe the kings doesn't really want succession wars,that could warn the population that the figureheads are a fake monarchs, or maybe just  like Historia, are not even aware that they are royalty when they are born, or those who refuse the selected heirs, have their memories erased by the power of the founding titan.