Here is a wild theory. Dragon shanks and teach are all half brothers.

Here is the theory. All 3 are the sons of rocks D xebec to 3 different women and here’s how.

1st Dragon. Dragon is the eldest, I’m new to reddit so I don’t know if I can upload pics to back this up but anyway when we see rocks there is a striking similarity between him and dragon. So here’s dragon section. When dragon was 17 years old he learned his fathers evil plan and manage to send word out to garp a marine who chased them around for several years he sent word of rocks plan to attack god valley which led to the marines intercepting them.

After the battle ended dragon was taken in by garp who trained him to be a marine. Dragon rose through the ranks and worked alongside akainu. He would meet garps daughter and the 2 would get married and have luffy. Luffy mother was a outspoken person who challenged the world government which led to her death which led to dragon forming the revolutionary army and garp to join sword. Dragon took his wife’s name out of respect to the man who took him in and to spare his family from carrying that name of Rocks.

Black beard To me black beard is the least likely to be rocks son because of how close he is.

Teach is rocks 2nd oldest son who is now 40 making him 2 when god valley happened. Teach mother was part of rocks harem and was a loyal supporter, if you want to know what she was like think of bellatrix lestrange from Harry Potter. When rocks fell she fled with her son to some country and fell into a life of poverty. She would speak highly of rocks to her son and when she died he went out and found his way to whitebeard the other man who betrayed rocks. We know the story since then. He took his mother’s name so not to raise suspicion as the marines would go after him non stop if they knew he was a Rocks. Shanks learned of this connection and went to meet the elders and told them about black beard and how they should focus on stopping him before he grows out of their control. When luffy leaves wano he will find a poster for him saying rocks D teach aka Blackbeard. Blackbeard has a similar goal to rocks and named his flagship the sword of xebec. Now because they went out of their way to explain how weird his body is I feel like there’s more to it than that.

Shanks. Oda releases a drawing of luffy at 40 years old and 60. At 60 he looks exactly like garp but at 40 he looks a little like shanks. Shanks being the youngest at 39 would have been a year old. Shanks mother was also part of the harem but would soon see his evilness and how far he was going. She manage to get into contact with roger who she encountered before. She summoned him to god valley to take down rocks. After the battle ended she left with roger as she was a wanted pirate and could not go with garp. Roger took her in as well as the baby shanks but he took note of garp taking in dragon. Roger brought them to the west blue to live in peace. A few years later he came back as he was in the area and learned she had died and left shanks alone. Roger took shanks in and gave him his straw hat and that is how shanks came into the picture.

Now as evidence. Shanks when he met with whitebeard was told that everytime WB sees his face his scar hurts. We are led to believe the man he was referring to was roger but in that case when doesn’t ace trigger anything as he looks like roger.

WB was referring to rocks. This is also why shanks has so much sway in the world government because they know he is rocks son and could reveal many secrets about them. These 3 brothers aren’t necessarily close unlike ace sabo and luffy.

So if this theory is true then luffy is the son of dragon and the nephews of shanks and black beard and the grandson of garp and rocks.