Thomas is still quite unsure about riding a bike. We've taken off the training wheels and he has identified "summer" as the time he plans to learn to ride. Consequently, he refuses to even try in the Spring.
I have told Tom that he is too big to ride his old trike, but I will concede as long as he is willing to tow Gordon. He's pretty good to share (after all, a trike is much less scary than a two-wheeled bike, even if you do have to give your brother a lift) and I caught them "sharing" very sweetly on the way home from the school.