Potty training: where one goes, the other will follow

Jonathan has always let Matthew take the lead in all things physical.
When Matthew was learning to crawl, Jonathan sat aloof, unmoving, in the center of the living room floor and watched. He watched for weeks as Matthew learned to fall from sitting position onto his belly, lift himself up onto his hands and knees, rock back and forth and then, finally, propel his body in different directions.
Two days later, Jonathan was at least as fast as his brother.
It was the same scenario for rolling over, sitting up and walking.
So I supposed I shouldn't be surprised that Jonathan shows no interest in potty training while Matthew is obsessed.
It started at the sitter's three days ago and Matthew's obsession has grown each day since.
This morning, he refused all potty seats and the toilet insert. Instead, he propped himself up on the big toilet and, for almost two hours, he sat and peed and sat and peed, watching Once Upon a Potty over and over.
He missed a few times and he didn't quite get there for number 2 (though he knew it was coming and he tried), but he had three or four successes (He drinks a lot.). Meanwhile, his brother sat on the sofa, aloof and unmoving, drinking milk.
For a moment, I thought Jonathan might join in. He stood up, pulled off his shorts and peeled off his diaper with an eager look on his face. I pointed him toward a potty seat and he moved forward, right past it to the Cars pull-up that lie on the floor next to it.
He handed me the pull-up and his shorts and said, "Cars? On?"
So I helped Jonathan into his pull-up, gave him more milk and turned back to Matthew, who was alternating toilet-flushing with toilet-sitting and hand-washing. Matthew was, once again, taking on the physical burden for his identical twin.
But he didn't seem to mind and, although Jonathan's eyes appeared glued to the little cartoon Joshua who was sitting on a little cartoon potty, I'm sure I saw his eyes shift to the bathroom every now and then.
So, for now, I'll focus on teaching Matthew.
And I'll let the brothers work out the rest.