So who was Poseidon?

Poseidons grandfather was Uranus, the god of the sky. His grandmother was the Earth, Gaia.
He was the son of two of the 12 Titans and his brother was Zeus.

everyone knows his power and kingdom, but few know about his weakness: women.
He has spawned quite some offspring. He changed himself into a horse to get the woman he wanted, his sister who had turned herself into a mare to avoid him.
Did you know he was the father of Pegasus? That was a result of a quickie with Medusa. I didn't know they had brown paperbags back then.

Because of this weakness it is perhaps why ships are called 'she', to please Poseidon. The maidens on the bows must have pleased him.
By the way, you don't want to know how Aphrodite was born and how nymphs came into the world.