The god of the sea we going out with medusa the monster at first they would be talking and then after a few dates he finally asked her out and most of the gods didn't agree with the relatonship that they had so Zeus the god of all Gods banished her out of no where to the undwerworld.
Poseidon was waiting for Medusa in the edge of the sea where they would meet everytime that they saw eachother. hours went by and she still didnt come at first he though that she no longer wanted to be with him. he went to his brother Zeus and Hades and told him that she left him and they said to forget about her and he did after the "help" of his brothers.
In the begining of time Meduas was not the monster that she was she was actually really pretty and with beautiful hair but with in thousands of years that she was left their to rot by Zeus and Hades she became really bitter and he beautiful hair became the snakes that she has in her hair now and got the power to turn anyone into stone with so much anger that she had.
Medusa was able to brake out of the underworld with the help of her new power. and when she broke out she wanted to get revenge on Zeus, Hades, and her love Poseidon but with anger she no longer loved him but deep down she did.
The three brother were hanging out and out of no where Medusa came in and was about to attack Zeus, and Hades until she saw Poseidon and half of her anger left when sh saw him and he looked at her and asked if it was his love from thousands of years ago and she said yes. long story shot they were still madly in love with eachother and asked what had happen to her.
The two brother had to appologize to Poseidon and Medusa to what they did thousands of years ago and with that they got to know her better and actually liked her and were happy that their brother found love and was happy with the person he chose to be with.