Portgas D. Ace, born as Gol D. Ace and nicknamed “Fire Fist Ace”, was the adopted older brother of Luffy and Sabo, and son of the late Pirate King, Gol D. Roger and his lover, Portgas D. Rouge. He was adopted by Monkey D. Garp as wished by Roger to him before his birth. Ace was the 2nd division commander of the Whitebeard Pirates and one-time captain of the Spade Pirates.
Hunted by the World Government for his lineage, Ace ultimately met his end two years before the current storyline after being captured and sentenced to death, which resulted in the Battle of Marineford in an all out clash of powers. Ace was freed, but he sacrificed his life to protect his younger brother from Akainu.
Ace was much more intelligent, polite, and generally more bearable than Luffy, which prompted the Straw Hat Pirates to question whether he was truly related to their captain. While several people who knew Gol D. Roger noted Luffy is quite similar to the late Pirate King, Whitebeard himself claimed that Ace’s personality was not at all like his father’s. It seems that among the very few things the brothers shared was their recklessness as pirates (and their near-bottomless stomachs). In addition, Ace liked to party as much as his brother does. When he boarded Buggy’s ship, he was drawn by the smell of food and decided to enjoy himself while he was there. Ace could be a bit inappropriate though as he once used a woman’s skirt to wipe his face while he was dining at Spice Bean in Alabasta.
There were two running gags about Ace. The first was his rather extreme narcolepsy. He tended to randomly fall asleep while eating and conversing, leaving strangers around him wondering if he had died. This was first seen in Alabasta when they thought he died in the middle of eating. The second was that he did a “dine and dash” routine wherever he went. This went back to his younger days with Sabo and Luffy, when they would often dine and dash in the city of Goa.
His “politeness” is due to Makino’s teaching after Ace asked her how to introduce himself to Shanks (being his brother’s savior). Before that, Ace was rather cold and rude to anyone he was not familiar with.