"Don't worry kid, you're dad had plenty of kids he stopped helping out when he lost interest"
Theseus, who was helped by poseidon multiple times, but in the end was thrown off a cliff by the citizens of Athens and drowned. Drowned in the ocean, the very domain of his father.
Kymopoleia, who was neglected by Poseidon once he found her to be too violent, left to wander his abandoned palaces, given up as a war prize to man she didn't even want with no choice at all.
Bellerophon, who was given the pegasus to tame as a gift from Poseidon in some myths, dying by falling off of it on his way to Olympus.
I'm just saying, that line wasn't a random throwaway line by Ares, he means it.