I don't think they'd have a child, but I figured I'd take a crack at designing a daughter for Sonic and Shadow anyway! Where Sonic is a runner and Shadow is a roller skater, Stellar is an ice skater/dancer! She's sarcastic and wisecracking much like Sonic, but is far less impulsive.
Shadow either looking at the ground trying to avoid eye-contact with everyone, or he's just staring at Sonic's hand like *huh, ok*
Contrast in expressions:
angy bf bf w/soft look
Question: have we ever seen a look quite like this before on Shadow in regards to Sonic? Like, it's hard to describe but his expression seems subtly different from all the others and I can't recall ever seeing it before. It's a unique expression that l'd dare say is soft in Shadow's own way