Well, the samurai title is practically a lineage, so for Ryonosuke and the others to be samurai would mean that at least one of their parents was one as well.
In fact the only one who's parents apparently weren't samurai seems to be Takeru, so if the whole kagemusha thing had not happened, the most Takeru could have been was a kuroko. A kuroko with unusually strong mojikara, but a kuroko nonetheless.
Did anyone else caught the fact that kagemusha plan originally was to wait for the 19th head (Kaoru's future child) to perfect the Seal? Only to have her perfected sooner than expected. Yet despite everything it was still the 19th head leading the attack that defeated Dokoku.