Have you ever wondered how many siblings Sonic the Hedgehog has? Well, I'm glad you didn't ask! To answer this question we'll have to look across many different continuities. (No there won't be pictures.)
First up is one of the various origin mangas for Sonic. It takes place in Nebraska, for some reason, and features Sonny who will later be redubbed Sonic. In this manga, it's stated that Sonny has a mother, a father, who died of radiation poisoning if I remember right, and five unnamed little sisters.
Next, we go to the games. While one? I dunno. Probably the second or third one if I had to guess. Anyway, there were going to be red and yellow playable hedgehogs that were also going to be Sonic's brothers. This feature was canceled.
And speaking of canceled! Sister Sonic was a game that was set to feature a female relative of Sonic. It was unclear what the relation was, most likely a sister or a cousin. She was going to be more mature than Sonic and have a flirtatious personality, keep this noted for later. However, the game was canceled, technically. You see, Sister Sonic was going to be a reskin of a game in Japan that was unknown here in the West. When the fans found out there was enough backlash the the game was released with the original story and character intact. No, I can't remember what the game was called.
Back into the mangaverse, we have Sonic's first actually named parents. (Isn't this exciting?) Paulie, who was a former test pilot turned pilot for the postal service, and Brenda his wife. They have two children ten-year-old Nikki, guess who that could be, and seven-year-old Tania/Anita. Why does she have two names? Well, evidently the lettering (conje?) got flipped. I reckon that Tania is still her canon name since her skirt has a T on it. It wouldn't be the last time the manga had a mix-up. In one issue Tania's royal yellow fur got swapped with Amy's pink. Tania was a bit of a tomboy who liked skating, skateboarding, and teasing people. Funny enough this might have been Amy's and Charmy's first appearances, even before their debut games.
Another honorable mention goes to Archie comics. While Sonic did have parents, Jules and Bernadette, and even an uncle, Charles. He didn't have siblings. There was one time a hedgehog, Tonic, claimed to be his long-lost twin separated at birth. But he was just trying to tick him.
Now for the cartoon that some of you have been waiting for, Sonic Underground. Sonic is a triplet this time. His mother, Queen Aleena, separated him and his sibling at birth. He ended up with his Uncle Charles, who had somehow ended up in this continuity. His sister, Sonia ended up with a rich archacrat while their brother, Manic, ended up being stolen from the front step of the family that was supposed to take care of him by a gang of street thieves. Sonia was actually meant to be the main character with Sonic fighting Robotnik IN SPAAACE! She was going to be more mature than Sonic with a flirtatious personality. (See, I told you those notes would come in handy.) Manic wasn't even going to be it. Which I guess is why Sonic and Sonia have powers and Manic doesn't. The series was canceled sadly.
In the Sonic cinematic universe, Sonic has Tails and Knuckles has his adopted brothers with Tom and Maddie acting as their parents.
In the main continuity, Tails is more or less his brother and, possibly, Knuckles as well.
In Sonic Prime it seems like this includes Shadow too.
And that's about all I could find. Now, what siblings are canon, well.... Pretty much all of them since the Sonic universe was revealed to be a multiverse. It depends on who you want to count really. Biological siblings in the media that officially met the light of day? Eight. Biological siblings in all media canceled or not, ten or eleven depending on whether or not you consider Sister Sonic to actually be Sonic's Sister. All of them? Fourteen. It's choose your own adventure.
EDIT: Someone pointed out Tonic is from Fleetway and not Archie. My bad.
