When they were kids they basically hated eachother, but only because of their dad's rivalry. I can imagine Shadow being super overprotective, Sonic too, but not as much.. As Clover grew up though she wanted to be friends with Spitfire but he always pushed her away, telling her how annoying she was, it might've stung but it never stopped her. She was determined to make things up, she didn't want their dad's to get in the way of a potential friendship. She'd occasionally tell her parents about him and of course Amy supported the idea fully, but Sonic, while he was never against the idea, he would often make jokes and laugh saying stuff like "Yeah sure Clo, you'd have to make the kid at least smile first, haha!!" Which he wasn't wrong, Spitfire never really showed emotion unless it was anger..

He'd always prefer to be alone, he'd often do reckless things, which worried Shadow and Blaze since he wasn't immortal like his dad. He always assured them he'd be alright though. While he'd never admit it, Spitfire was always a little jealous of Clover, after all she was caring, had friends, siblings and the village loved her, she had a good life, not that spitfires was terrible, but a bunch of people were straight up terrified of him, sure, he was intimidating but that felt like a little too much.

One day Clover set out to go talk him again, but instead of the usual arrogance she got "you know, Clover, you're not half bad." He finally realised how persistent she was, how strongly she felt about their friendship. She was quick to snap back with "Aha!! So you CAN be nice to me!!" Spitfire smirked "tch, dont ruin the moment.."

From then on they got closer even though she teased him a lot and he found her barely tolerable sometimes XD.