I saw a kind of "family tree" somewhere where the students of O Sensei were "divided" into three generations, depending on when during O Senseiīs teaching they were studying in his dojo. His students "grew up" and founded their own dojos. But students who were at O Senseiīs dojo in the early days of aikido had trained in a somehow different aikido than the students of the last generation because O Sensei never stopped improving aikido.
I think itīs natural that all these students developed their own style in some degrees because they were training at different times. If you see demonstrations by different sensei and compare them with old videos of O Sensei, you can still tell this "generation effect". Apart from the fact that O Sensei himself incouraged his students to try out their own ideas to improve aikido in general.