So i had the idea, and looked at the master thread where i didn't see it, if it is there i am sorry and i over looked it. But Polycephaly is the condition where - mostly in animals - a creature is born with two or more heads where they would usually only have one. I realize we have the conjoined twin mutation, and they are looking at working on a duel sided chimaera mutations, but i have not seen the idea of hydra headed cubs, i think how i would suggest it work would be as follows.

A cub would be born with two [or three heads] growing from two [or three] necks from the shoulder, one head looking not to alive or 'frozen' the other showing signs of normality. both heads sharing the same colors, eyes, and nose types, or often when Polycephaly is a thing, some animal's extra heads are shown limp, dead, or blind, so maybe have the extra head [or one of them] be as such, so maybe white eyes. This would be a lethal mutation causing the cub to die at one year.

The other way this could work could be a none lethal, and where the cub grows up to adult hood with several heads within reason, and they live a full life, but i feel this would be a had less realistic, though there have been some animals to live into full adult hood with polycephaly.

Thank you for taking the time to read, again if this has been suggested before, or is on the master list, i haven't seen it or over looked it by mistake.