You were a mortal baby boy. Your parents decided to leave you because they couldn't afford to take care of you. So they left you by the sea with a small letter saying "take care of our baby" and that's when Poseidon found you. He quickly picked you up in his arms, rocking you

"Now…who would let such a cute baby here…Awh…you're too cute. I'm not leaving you here"

So he took you back to Olympus with him. When he arrived he called for his brothers, Zeus and Hades.

Poseidon: "Zeus! I found a baby!"

Zeus: "Wha-wait what?! What do you mean you found a baby?! Where?! How?! Whose baby is it?! Why did you take it?!"

Zeus was very shocked and confused. Hades as the older brother spoke more calmly yet equally confused.

Hades: "Poseidon...why would you take a stray baby you found at the shores…? What if their parents are searching for him or...her?"