This is a very suprising theory. I mean, they look unrelated because Ariel's hair is red and Hercules's hair is brown!
But, this article will clear everything up.
Ariel's Genealogy Edit
King Triton is the father of Ariel and Ariel's mother is nameless and deceased.
We can show this with a Punnet Square of Ariel's genealogy.
K= King Triton
M= Ariel's Mother
S= Ariel's Sisters
Hercules's Genealogy Edit
Zeus is the father of Hercules and Hera is the mother of Hercules.
We can show this with a Punnet Square of Hercules's genealogy.
M= Hercules's Mother
How It All Connects Edit
King Triton and Posideon are connected because they are both all-powerful rulers of the sea. Posideon is one of Zeus's brothers.