I am not really sure if they are or not. The writers have seemed to have left that one open ended. I would like to know who Scootaloo lives with since she lives in a really nice house in town.
Not biologically, but they call each other sisters. Heres a bonus Scootaloo doesn't have any family, so I'm guessing that Rainbow Dash adopted her in her own way. Thats what I think.
This isn't canon but... I think Scootaloo lives in a cardboard box. Well, it doesn't have to be a literal cardboard box, but maybe an abandoned building or under a bridge. She goes to school and hangs out with her friends acting as though everything is normal but she's actually a homeless orphan. Honestly it does seem like that is implied. All the other ponies, both CMC and Mane 6, have had their family/backstory explained, except for Scootaloo. Same reason why she looks up to RBD so much and wants her to be her sister...because she doesn't have any parents or older siblings of her own. It is, in my opinion, the most fitting explanation.
This actually makes alot if sense. Though, she could also live in an orphanage, she doesn't have to be homeless.
And so many headcanons were lost that day. So many hearts broken ... because ... Scootaloo has a home? ... >.> ... Anyway, biologically I doubt them to be sisters. Though RD has become an apparent sisterly figure in Scootaloo's life. Someone Scoots looks up to, admires. She strives to be like RD which is commonly seen in younger siblings ... but wait until Scoots hits the rebellious faze (Season 22 Episode 13, Scootaloo Flies Solo). So for all intents and purposes, yes they are sisters. Applebloom has Applejack. Sweetie Belle has Rarity. Scootaloo has Rainbow Dash. Every CMC gets a sister, just this once! (vague DW reference) Seriously though ... how many people's hearts were crushed because Scoots actually had a home? That's just awful ... not that Scoots has a home but that people would be sad about it ... Although it would've been kind of cool to see the ep where RD adopts her ... I'm so heartless.
No offense but this seems silly to me. I'm pretty sure that if Scootaloo was Rainbow Dash's sister, it would've been brought up in season one don't you think?
no they are not but scootaloo really looks up to rainbow dash and rainbow dash likes her as a friend they have a somewhat sisterly relationship sometimes but they are not sisters.