All known ’D' characters from one piece and theories.

1. Gol D. Roger

Gol D. Roger Also known as Gold Roger in the OnePiece Universe was the Pirate King and owner of Legendary Treasure OnePiece. He is also the Captain of the Roger Pirates. The whole story of OnePiece is based on the main character Monkey D. Luffy going after Legendary Treasure OnePiece that pirate king has hidden somewhere in the world. Gol D. Roger is also the father of Portgas D. Ace (Brother of Monkey D. Luffy and Sabo) and Husband of Portgas D. Rouge. He is another character in one piece that is still a mystery. It's not confirmed whether he had devil fruit or not hence, even his powers are not known yet. Although some of pirate king's crew has been shown in the anime nothing has yet been revealed except for some of the rayleigh's power.

2. Monkey D. Dragon

Monkey D. Dragon, commonly known simply as "Dragon the Revolutionary", is the father of the StrawHat Pirate Captain Monkey D. Luffy and the son of the Marine
Vice-Admiral Monkey D. Garp. He is the also the leader of the Revolutionary Army who has been continuously attempting to overthrow the World Government. He is the most wanted man in the OnePiece world. Even though Dragon has been shown to be a fearsome character, His powers have not been shown yet.

3. Monkey D. Garp

Monkey D. Grap is a famous Marine Vice-Admiral who is also known as the Hero of the navy. He is given the name of "Garp The Fist" as he is famous for using his hand and punching just like how Sanji is with his leg. He is also the father of Monkey D. Dragon and grandfather of Monkey D. Luffy. Even though Ace was adopted by Garp he still calls Garp as his grandfather hence, He is the Grandfather of Portgas D. Ace. Garp is one of the legendary famous characters just like Shiki,Gol D. Roger, Whitebeard, Sengoku etc. Even though he has shown us a few his powers his true powers are still unknown to us.

4. Portgas D. Ace

Portgas D. Ace is one of the most famous and fan favorite character of Onepiece. He is the son of the Legendary Pirate King Gol D. Roger and Portgas D. Rouge. He is also the sworn brother of Sabo and Monkey D.Luffy. He was the captain of Spade Pirates and later became the 2nd Division Commander of Whitebeard Pirates. He was the devil fruit user of "Mera-Mera no Mi". He has a bounty of 550,000,000. He was recently captured by Navy and was killed by Akainu in the same Marineford war.

5. Monkey D. Luffy

Monkey D. Luffy is the main character of the series. He is the son of Monkey D. Dragon and grandson of Monkey D. Garp. Monkey D. Luffy is the brother of Portgas D. Ace and Sabo. He is the Captain of "StrawHat Pirates" and dreams of becoming the future pirate king and finding the legendary tressure OnePiece. He has a bounty of 500,000,000. He is also part of one of the worst generations.

6. Trafalgar D. Water Law

Trafalgar D. Water Law is one of the members of the worst generation just like Monkey D. Luffy. Law has a bounty of 500,000,000 as well. He also had the title of a Warlord for short amount of time. He is the Captain of "Heart Pirates". He is also the doctor of his crew and a devil fruit user of "Ope-Ope no Mi". Law is also known as the "Surgeon of Death" as he got the heart of 100 pirates to get the title of a Warlord.

7. Portgas D. Rouge

Portgas D. Rouge is a unique character that has just been introduced once in the story of OnePiece. She was the lover of Gol D. Roger and mother of Portgas D. Ace. She is a mysterious power and so is her background. The only information is known to us till date is that she used to live in South Blue.

8. Jaguar D. Saul

Jaguar D. Saul is also one of the characters whose power is still a mystery. He was also a Vice Admiral of the navy. He is the only known Gaint character having initial D in the whole Onepiece story. Saul was shown to be killed by Aokiji when he tried to save Robin in Ohara. It was only portrayed as he died but it has not been confirmed that he is dead. Nothing regarding his past or powers has been revealed yet in Onepiece.

9. Marshall D. Teach

Marshall D. Teach also known as "Blackbeard" is also one of the main characters in the OnePiece Storyline and seems to be the final villain of the storyline as well. He is the only guy who has consumed two devil fruits in the history of OnePiece. He is now the Owner of Gura Gura No Mi and Yami Yami No Mi and is now having the Status of a Yonko. He has not been shown using Gura Gura No Mi much but he said that he still has to get used to that devil fruit But he seems to have awakened devil fruit power for Yami Yami No Mi. He used his awakened devil fruit power when he fought against Ace, Whitebeard, and Magellan. Blackhole which seems to be his special move seems to be the result of his awakened devil fruit as he turned the entire surrounding into darkness and just like blackhole it could consume anything.