If you are not familiar with the Percy Jackson books then you will probably not understand this preference.
Calum would be a son of Aphrodite but would blessed by Hermes, Apollo, and Dionysus. Calum has the ability to make anyone fall in love with him but his weakness is that he refuses to intentionally break anyones heart.
Ashton would be a son of Athena but would be blessed by Apollo for his advance knowledge of musical instruments. Ashton would be skilled in battle as well as useless information. Ashton is skilled with a bow and arrow but he prefers to use his sword.
Luke would be a son of Apollo, [as would Niall Horan] he inherited his father's eyes and golden hair. Luke also inherited the ability of Vitakinesis, the ability to heal by singing. Luke would be surprised to learn that he is good at archery, and would much rather attack his enemies from afar with arrows than to physically attack them. Luke would actually be proud of sharing the same name as Luke Castellan as he heard of how the demigod became a hero in the end. Luke is one of the few guys blessed by Artemis.
Michael would be a child of Hermes [as would Louis Tomlinson], despite that most people think he is a child of Hypnos since he sleep so much or a child of Iris since he has colorful hair. He is known for causing mischeif with his half brothers Connor and Travis Stoll. Michael would have great fighting skills and wouldn't be afraid to attack anyone who dare harms a certain child of Apollo.
Author's Note: Comment below if you want me to write about the 5sos boys going on a quest together. [To be honest, I think all of the Five Seconds of Summer lads would be blessed by Apollo even if they aren't a son of Apollo.]