Kirk's brother Sam was in an episode of TOS. The story where giant pieces of skin flakes flop down from the ceiling and fly onto people's backs, sting them, and become parasites. Spock becomes infected and goes on a rampage.
Sam Kirk was a biologist and was killed in this episode. He's kind of infamous in Star Trek fandom because he's played by William Shatner, just with a mustache and dyed hair.
So there is precedent here. Might as well ask if it's hard to fit Pike, Uhura, and Nurse Chapel into existing frameworks.
But I do not want to see a "who's who" of TOS characters being shoehorned into the series. I really hated that on Picard. I'm guessing that Beverly Crusher makes an appearance on S3 of Picard, along with a couple other regulars from TNG, like the Bajoran helmsperson.