They worked well together.
Anyone could see it. In a way, they were parallel to Sherlock and John, but at the same time not. Very, very not.
Seb changed Jimmy. Told him he could fight back and win. Seb was the one that helped with Carl Power's. Seb was the one that taught Jimmy that if you get hurt, you hurt right back.
Jimmy helped Seb. After they met up again as adults Seb was going into a downward spiral of gambling and alcohol and not coming out. Jimmy made those problems go away.
But Jimmy was controlling. If he liked you, you couldn't escape. If he was just using you, you still couldn't until he was done. And Jimmy really liked Seb.
Seb liked that. He listened to orders, he didn't give them. He liked being Jimmy's favorite pet. (And he was his pet, not his toy. There was a fine line between the two, but they were still very different.)
Yes, they were Jimmy and Seb. Seb and Jimmy. It certainly had a nice ring to it. Certainly better than Sherlock and John.
Together, they would beat the new plaything, completely destroy him…
But not before some fun.