Scout's official bio says he has seven older brothers (Note: None of them have appeared in any canon TF2 material or even mentioned by name. This bio is the only proof they exist).
That said, one question has been invading my mind:
Is Tom Jones Spy their father as well?
Probably not, the implication is that either Scout’s mom just had bad luck falling for men who didn’t stick around. (TF2 comic spoilers)
Spy's supposed to be a deadbeat, so I don't imagine he'd stick around eight years before dipping - also, that means that Scout's brothers would have known who their dad was, and they would have told Scout. Also, Scout's large quantity of children in the final comic is meant to be a parallel to his mother, and they are all to different women. So no, I think Scout is the only son of Spy, at least to Ms. Willis.
Valve probably forgot they even existed so never thought about Spy's relation to them.
Spy probably sends secret checks to Scout's mom after he met her (since we dont know if she ever was employed, 8 kids must not leave a lot of time for work and cost a fortune in time and patience)
BUT
We dont know when Spy and Scout's mom strated dating, and how long in the relationship Scout came around or how many brothers there was around already
Also i imagine Spy knowing full well the names and addresses of Scout's stepdads, but never done anything unless Scout's mom asked him to
Maybe he disguised himself as an uncle to come visiting from times to times ? His spytech would be handy to do Santa stuff
Dammit I think i established Santa might use spy technology in the TF2verse
It’s the other 7 mercs and they’re all brothers through Spy who fucked all their mothers
I love that you used a spoiler tag.