In the Poseidon cabin their are 4 brothers, 4 full brothers, you see Poseidon really loved their mom so he had 4 children with her.

The first child is Minseok or Xiumin as most people call him, Xiumin has the power to manipulate the temperature of any liquid and that includes blood so i wouldn't mess with him, his brothers or his crush Luhan, because if you do well you could end up freezing to death or over heating to the point where you  can't survive anymore because your body tamperature is too high.

The second son  is Junmyeon or Suho. Suho can maipulate any liquid in anyway that he wants, luckely Suho has a calmer temper then his older brother but i still woulden't mess with him as he could make all of your blood exit your body through any opening he wants, like through your mouth, nose, ears or even your eyes.

The next child is Jongdae or Chen and he has the worst temper of all 4 brothers epecially when you mess with his boyfriend Baekhyun. Chen can cause earthquakes when his temper gets to much and one time Barkhyun had gotten hurt and lets just sat that the Ares cabin had to find other acconidation for a while.

The final child and the youngest of the 4 is Jongin/Kai and he is the calmest and chearful of all 4 brothers. Kai has the power to water trave, water traveling is simular to shadow traveling, but you need to be in water to water travel so Kai cann't use his power very much. 

To begin with they would always fight over where they would sleep in their cabin but now they have actually sorted out their sleeping arangemnts. They desided that the 2 oldest brothers suold get the top bunks and the younger 2 sould take the botton bunk so you have Xiumin and Chen on one bunk and Suho and Kai on the other bunk.