I´d say it´s possible they are from different family branches, if they are related at all, also about Overhaul´s quirk, I think it´s just some kind of blood manipulation quirk and not just plain cell destruction, because we already have Shigaraki´s quirk for that, for melding there´s also Class B´s Awase quirk, so we have these basic quirks when it comes to straight up creation of non organic objects, desintegration and melding, Overhaul´s quirk seems a bit too complex to be too much related to Momo´s which is why him being from a different family branch could explain the bigger difference between his and Momo´s quirk abilities.
Another thing, that has been bothering me for a while, but in the initial BnH episode when Momo was introduced she had the exact same eye color as Overhaul, I dont know if that was some sort of red herring or foreshadowing, between the two but the option is certainly out there.