It’s been implied that Sour Cream and Onion are Half-brothers
Yellowtail, Sour Cream, and Onion are all seen together in The Return, implying they are a family unit of some fashion.
Vidalia is a type of onion. Vidalia is likely Sour Cream and Onion’s mom, completing a terrible trifecta of names.
Sour cream talked about his “weird step dad,” which likely refers to Yellowtail, meaning Sour Cream’s genetic father is unaccounted for.
The timeline is a little hazy, but if Sour Cream was conceived when Marty was in beach city, the difference between Steven and Sour Cream’s age would be the amount of time Greg and Rose dated before deciding to have a child, Which seems like it checks out.
Where else do we know onions from in Steven Universe?
This creepy kid. But we are very aware of who his father is. The fisherman
But this man is not Sour Cream’s dad, it’s his step dad. We also know that the Fisherman has a distinct problem with Sour Cream being a DJ. But what if he has a problem with the entire music industry? Why would that be? I want you to look at these two characters and tell me there isn’t a resemblance.
Marty is Sour Cream’s biological father, the scene introducing Vidalia following conception (and in Greg’s van you sick fuck). But what if Marty never came back to Beach City, leaving Vidalia to raise Sour Cream on her own at what appears to be a relatively young age? After she marries the Fisherman, he would know about this story and be worried that Sour Cream would go down that path as well.