(My own alternate universe)
(This Steven is 14)
(If you're curious his tumblr is @mystery-steven)
Basically he was dropped on the side of the road as a baby and was picked up by Garnet, took him home and cared for him. But once he got to the age of 4 his eye got scratched out by a gem. He now has a pink eye and a permanent scar on his face. Now his gem parents are teaching him not to go outside. He is now very shy, but very kind and fragile hearted

Scenario 1
You were on the beach one day, when you see a human kid wandering through the sand that you had never seen before. That's when you see Pearl jump in and take him inside...

Scenario 2
Make it up