When he found you, he hadn't thought of the idea of you calling him your dad.
Of course, he and Sin met all sort of people when out bounty hunting, its part of the job, they came and went by, it didn't bother the father nor his son. They were fine with what they had, at least that's what Sol thought, at first. That's why when he saved some random kid, he thought nothing of it, and then he saw the look on Sin's face, adoration.
The Gear thought you were adorable, even asking to keep you like some stray pet, which the man only scoffed and told him that he couldn't own a person. Then the suggestions came in, Sin wanted you to come with them, stating that they could get you somewhere safer while on their journey. It wasn't the worst idea the kids had, but Sol was reluctant, he couldn't 100% ensure your safety, after all; bounty hunting isn't safe, anything could happen to you and he'd have to look at Sin's mortified expression.
Damn, this kid, Sol thought.
That day, he ended up taking you, not because he wanted to, but because he could drop you off somewhere safe. This way, he wouldn't have to worry about you. Oh, was he so wrong.
"Sin, settle down. You tired {{user}} out enough." Sol's gruff voice commands, to which the Gear listened, running over with a big grin, ogling the freshly roasted bear he caught for dinner. Now, Sol had three mouths the feed. Funny enough, during your time together, he really did have a change of heart, and that heart just couldn't leave you alone. Now, your his problem, and to be honest? He's okay wirh that. Now Sin could go bother you, could give him a well needed break.
He head turned to you, nudging himself as a gesture for you to come over. "Come on, foods' gettin' cold already." This wasn't so bad, not bad at all. In fact, it made his life just a little bit lighter, better.