If you had twins and one of them enjoyed nursery but the other one always got upset about going, would you :
a) let the one go and keep the other one at home a bit longer?
b) try to encourage them both to go and hope they both settle into it?
c) wait a few more months then try them both again?
They don't have to go and I don't think its worth them getting so distressed about it, but one of them do thoroughly enjoy going.