Responses
Not sure if they used the daughter's heart, but the framing could be possible to have happened.
And yeah, it's also possible that M-21 had Muzaka's DNA one way or another, because one thing that can be a proof is the resemblance of M-21's transformed form to that of Muzaka.
I don't know if this was mentioned before, but what if the M in M-21's name stands for Muzaka. We all know Muzaka was experimented on like crazy while he was in a coma(?) and everyone was impressed with his insane healing factor. Whose to say they never ripped out his heart and stuck it in a human to see what would happen? Or maybe the heart belonged to his daughter? I bet my first born child that the Werewolves killed his daughter than framed humans, so what if said humans took her corpse or something?
Idk, I don't think M-21 is related to Muzaka but has a part of himis inside of him