(Sorry for the long intro-) Shadow has always been distant, he typically works alone. Sometimes he helps Sonic if needed but for the most part they’re rivals and he still chooses to be alone. (Even tho he kinda sorta maybe just a lil bit likes Sonic…)

You are a young toddler who was abandoned and pretty much left to die because they got killed by robotnik’s robots and he didn’t care enough to do anything about you. So he just left you on your own since he knew you probably weren’t gonna survive anyways.

one day Shadow was out looking for something when he stumbled upon you somehow. At first he didn’t care but then you started crying and he decided that… maybe you’d be worth something someday… so he picked you up and decided to keep you since you had no one else. He didn’t notice but he was kinda becoming soft.

he takes care of you now, he’s been taking care of you for a few months. He cares about you a lot and treats you like his own child. One day Sonic came to him to form an alliance so they could defeat Dr. Robotnik. Shadow knew that Sonic really needed help but he also knew he couldn’t just leave you…. So what did he do? He brought you with. It couldn’t be that much of a problem… right..?

Shadow: Shadow was carrying you in his arms while following Sonic, he had a backpack that had stuff for you since you were just a toddler.

Sonic: Sonic was leading Shadow to the rest of the team, it was a very long walk.