One Piece theory suggests that there is one more member of the D clan within the Straw Hat Pirates.

SUMMARY

The Will of D. has resurfaced as a topic of discussion among One Piece fans, as Dr. Vegapuk pointed out in his message.

At the moment, Monkey D. Luffy, the main character of One Piece and captain of the Straw Hat Pirates, is the most popular member of the D clan.
There is an internet theory that Eiichiro Oda may have hidden one Straw Hat member in plain sight who, like Luffy, has the Will of D.

The Will of D. has finally become a topic of discussion once again amongst the One Piece fanbase, as Dr. Vegapuk has mentioned it in his message that is being broadcast to the world. However, before Vegapunk’s message could have revealed something important about the initial D, it was stopped from being broadcast by the Five Elders.
Robin Discussing the Will of D. | Toei Animation
By the looks of it, it feels like the characters with the initial D in their names are going to hold a very important place in the entire final saga of One Piece. They have already created enough mystery, and among them, the most popular member of the D clan right now is Monkey D. Luffy, the protagonist of One Piece and the captain of the Straw Hat Pirates.

Although officially he is the only member of the crew with the initial D in his name, there is a theory on the internet that states that Eiichiro Oda might have hidden one Straw Hat member in plain sight who, just like Luffy, carries the Will of D.

The Mention of the Will of D in Vegapunk’s Message

The past few chapters of the Egghead Island arc in One Piece have focused on a shocking message that Dr. Vegapunk has been broadcasting to the entire world. This message has contained the answers to some of the most important mysteries in the world, from the Ancient Kingdom to the character of Joy Boy.

However, the most important revelation that Vegapunk was about to make was during the conclusion of the message, where he specifically denoted a special piece of the message to the members of the D clan. When he mentioned the people who carry the Will of D, it turned a lot of heads among the prominent members of the D Clan.
Vegapunk Talking About Will of D | Viz Media
As soon as he was about to explain something important, the broadcast was stopped by the Five Elders, leaving the One Piece fans and characters in anticipation of the inherited will of D. This has led to the development of multiple theories where fans have tried to figure out what Vegapunk could have relayed to the D clan members.

One Piece Theory Hints at Another D Clan Member Among the Straw Hat Pirates

There is a popular theory going around on the internet that states that the Straw Hat crew might have a member with the initial D in his name other than Luffy. This member is none other than Franky, the shipwright of the Straw Hat Pirates. There are a few pieces of evidence that support this bizarre theory.
Franky in One Piece | Toei Animation
The first and foremost clue is in his real name. Franky’s original name is Cutty Flam, which can also be read as Cut D. Flam, just like Gol D. Roger’s name, which was changed to Gold Roger to hide the fact that he was a member of the D clan. Franky’s name has been foreshadowed in the narrative, which makes it even more probable.

Another element that hints at Franky carrying the Will of D is his personality, which is quite similar to Luffy’s. Both Luffy and Franky are carefree and do not care much about things. They do what they feel is right, and this draws other characters towards them and helps them find an ally within them. Therefore, there is a big chance that Franky can be a D-clan member.