Board Thread:Questions and Answers/@comment-29752445-20180827202712/@comment-26495049-20180830050407

Narutoka5 wrote:

but we think that the most probable answer is that once ymir died the 9 succesors ate her body (we can see a hint of that in the ending of season 2) which 3 of those 9 were her 3 daughters, and we believe the daughter, and each one of the 9 got one of the shifters power, and we believe that one of the 3 daughters inherited the founding titan power, by "fate" I guess, and then that daughter's bloodline and descendants are the "royal blood". That's what I think too. Since Ymir Fritz was the originator of the Titans, it's possible that the first "inheritor" of the Founding Titan would be "selected" as the royal family (i.e. only their descendants can use the Founding Titan).