Ace Sabo Luffy

Ace, being a fellow child who wants to be a pirate, was a good friend of Sabo's. In fact, they were like brothers, and Sabo was willing to forsake his dreams to save Ace and Luffy from his father's wrath. It is unknown whether or not Sabo was aware of Ace being Gol D. Roger's son, though in the anime he was fully aware of this fact, as well as the one who informed Luffy of it.
Two years after Ace's death, Sabo deeply regrets that he wasn't there to try and save his brother's life, and after discovering Ace's death in the paper, he was devastated. He visited Ace's grave and left three cups of sake next to Ace's gravestone in memory of their brotherhood, and pinned a newspaper article to the gravestone to indicate that Luffy is doing fine. Despite his regret, Sabo still remains determined to inherit Ace's will by obtaining the Mera Mera no Mi. He later looked to his late brother to watch over him as he entered the arena. Sabo obtained and ate the Mera Mera no Mi, and the first attack he used with his new abilities was Ace's signature move, Hiken.