Who are/were the highest ranking aikidoka, and what was their rank!? (I presume O sensei was the highest rank - 10/12 dan?)
See Aikido FAQ at:
for info on Aikido 10th Dans
O Sensei (Morihei Ueshiba) was the founder and was not considered within the ranking system, just like his son and grandson, who are/was head (Doshu) of the Aikikai organization.