Too Much Math
Don’t you love it when a character from a movie plays a role in another movie’s lore? Well, this one might not be very exciting. The theory goes like this: Captain Hook from Peter Pan murdered Ariel’s mother. What evidence is there to back up this outrageous, childhood-ruining claim, you ask?
In Peter Pan, we see three mermaids, one of whom looks strikingly similar to Ariel. This, according to the OP, was Athena, who is Ariel’s mother. Later on, the pirates would slay the mermaids at Captain Hook’s command. Thank you, Captain Hook, and thank you, theorist, for pointing out something that we never wanted to know.