You just can't dislike this guy.With the perfect sense of humour which includes times of very lame jokes ,he is the perfect guy to be friends with. His friends include the son of Posiedon-Percy Jackson,the son of Zeus-Jason Grace,the son of Ares-Frank Zhang,the daughter of Athena-Annabeth Chase,the daughter of Aphrodite-Piper Mclean and the daughter of Pluto-Hazel Levesque.
These seven people comprise of the seven demigods of the Prophecy of the Seven.

GETTING BACK TO LEO -
Leo is one of the main protagonists of the series-Heroes of Olympus and is one demigod out of seven of the prophecy.He is the son of Hephaestus and is said to be the only living son of Hephaestus who is able to generate fire.

HIS HISTORY
Leo has a history which is very crazy and weird for a 15 year old.

Leo was born in Houstan,Texas on 7th of July to mechanic Esperanza Valdez.When he was little,he had a babysitter named Tia Callida,whom later was discovered to be Hera in disguise.She was watching Leo because she knew of his destiny as

 one of the seven in the prophecy. She tried to "kill" him by putting him in an active fireplace and by letting him play with knives. She also tried to make him poke a rattlesnake, which he refused to do. 

This was done to help train Leo to be strong at a young age. He once drew a picture of a flying boat with a bronze dragon head as the masthead in crayon at the age of five and just as Leo was going to sign his name on the picture, it was blown away by the wind. 

Tia convinced him to use his abilities to start a fire to "warm these old bones," and he ended up burning his fingerprints into the table.

At the age of eight, Leo was visited by Gaea,

 the Earth goddess, whom intended to break his spirit, after being notified by Medea that he would have a part to play in her downfall. Horrified, Leo tried to use his pyrokinetic abilities as defense to save his mother and himself, but Gaea manipulated the fire, burning the mechanic shop. His mom died in the fire, and his Aunt Rosa turned his remaining family against him, thus forcing him to be sent to several foster homes.

The death of his mother haunted Leo for years. The emotional strain caused him to run away from multiple foster homes. After running away for the sixth time, Leo was sent to the Wilderness School, where he met Piper McLean, who unbeknownst to him, was a daughter of Aphrodite.
 When Hera switched Percy Jackson and Jason Grace, she manipulated the Mist so Leo would think Jason was his best friend, although they became real friends later on. He is said to be the only living son of Hephaestus that is able to generate fire.

APPEARANCE
Jason describes Leo to look like a "Latino Santa's elf".He has curly black hair,dark brown eyes.pointed ears a cheerful and usually a mischievous smile on his face.He has an average height of 5'6.He has a scrawny build.He has a look in his eye which makes him look like he has taken more caffeine than the normal limit .Annabeth says that he has more ADHD than normal demigods.

PERSONALITY

Leo is easygoing, upbeat, energetic, funny, flirty and loves to tell jokes constantly, even if they aren't particularly funny. Leo is genuinely very intelligent and honest, and cares about his friends and family. He sometimes doesn't think before reacting and he enjoys pulling pranks on people, especially those who he doesn't like. Despite his jokey attitude, Leo is emotionally scarred from the death of his mother and is crushed by guilt as he indirectly caused her death. He hides a hurt and angry demeanour with humour. Leo has been shown to have a serious side, which happens when he is angered by someone or when the situation calls for it. He is also seen building small bits of machinery and equipment and is very skilled and serious about his work.

SOME MORE FACTS

• Leo can speak  Spanish,English and Greek fluently.
• Leo has ADHD (more than the other half-bloods) and Dyslexia.
• Pyrokinesis it is the ability to control fire well as being completely immune to being burned by fire. Leo Valdez has this ability and uses it to protect himself as well as others. 
• Leo's favourite colour is red