This is not for those sceptic of him being alive so if you will comment, I'll ignore every comment you post.
So after Sabo's ship was destroyed by the World noble he fell uncoscious and stayed afloat on a plank of wood from the wreckage.
A ship comes by and Dragon stands on the ship watching the waves clashing against it when he suddenly spots Sabo.
Dragon: Men!!! I found a boy floating on the ocean!! we have to get him on the ship.
A crewmemeber looks at the boy: Dragon, this is a nobles child! we can't take him aboard, he's what we're fighting against!
Dragon: Indeed, but yesterday I saw him, he tried to warn the people of Gray terminal. I was engrossed by how mad the nobles have become, now TAKE HIM ABOARD!!
The crew lower a smal robe with someone tied to it, the man grabs Sabo and he see his hat floating with the wood and decides to take it too. Then they lift him and Dragon takes the child in his arms, puts him down on the deck and calls the doctor, the doctor comes there and Dragon: Will he be alright?
Doctor: With such wounds... but I believe we can delay his death at least, but if we get real medicine and equipament until tomorow he would have some chances of survival
Dragon lifts him and starts carrying him to the infirmary: C'mon doctor, we gotta hurry to the next island.
After one week Sabo wakes up on a bed.
Sabo: Ow, my body feels so beat up.(he says with a semi-loud voice while puting his right arm on his shoulder)
He looks around and at himself and notices he has badages: What the...? Why am I like this?.....Where am I?..... Man wha-(he remembers what happened and how he was almost killed by the world noble) yeah...so thats why I am like this...
Dragon enters the room with his cape lowered: Oh, so it seems you are awake now(he smirks)
Sabo: And who are you?
Dragon: I simply a man that felt the need to save you
Sabo: ...wait!....you're the one who listened to me from the Goa city! that ossan that said he knew about the fire!
Dragon: Yes, it seems you remember some things, I hope you will recover completly, after we found you at sea on a some scrap wood, I was pretty surprise myself...
Sabo tries get down from bed, but Dragon stops him with a hand on Sabos shoulder, Sabo screams of pain and falls on the bed...
Dragon: You'll have to wait a while until you can get down from bed
Sabo: I want to see my friends!! I want to know they're alright!!!!
Dragon: Your friends?
Sabo: Yes!! I wanna see if Ace and Luffy are alright!!!
Dragon: Ace, Luffy? you are friends with those two?! (Dragon starts laughing)
Sabo: WHATS SO FUNNY?!?!?
Dragon: (still laughing but not as hard) it is, because luffy is my son and Ace....(laughs and sits down on the bed)
Sabo looking very surprised and amazed: You're Luffies father?!!?? I didn't even know he had a father.
Dragon: Yes(he stops laughin but maintains a smile on his face) so you know them...
Sabo: Why doesn't Luffy even know he has a father?!
Dragon: My ambitions aren't good and for that, my son might be caught and locked just for being my son, its better for to not even know he has a father
Sabo: Ambitions?...locked up....just for being your son?! do you plan to be a pirate?!
Dragon: I won't be a pirate, I have other plans(he looks at Sabo) kid, do you hate the nobles?
Sabo: eh? (threw his mind small flashbacks come and he begins steadily with each moment to cry) I....I DO HATE THEM!!!
Dragon smirks and calms Sabo down: Kid, do you want to join my cause? I plan to destroy the world governament, there are even bigger nobles that kill without remorse, take humans as slaves, think we're inferior and law allows them to do so
Sabo looks shocked while crying: They're allowed to kill people?
Dragon: They can shoot whoever they want, do whatever they want, even if(Dragon gets angry) people just don't bow down to them
Sabo: But....thats....thats just....horrible...
Dragon: What is your name?
Sabo: My name is Sabo(he remembers his parents calling him so)...no...my name is now Henka (Changed)
Dragon: Henka it is then.
Sabo: But where exactly am I?
Dragon: You're on the Grand Line, in our headquarters, so Henka, want to join my cause?
Dragon smirks again and with a loud voice: WELCOME!