Simply question....do you think that Splinter was part of the foot clan?

[Luckyday]

From the past he and Shredder use to be friends. Could they also be part and serve in the same clan back in the day?

I don't know what the ninja clans are like in Japan in this show but if a rival and weaker clan knew that Shredder was in the states to hunt down Splinter and having trouble then maybe they would try to help Shredder's emeny if they heard that Splinter had started his own clan with powerful ninjas.