Waiting for a Bedtime Story

Bedtime can be hard work. One or other of my Monkies can decide to throw a wobbler or just be difficult. We have been having an issue with Carys wanting to squeeze William really hard when he comes for his bedtime kiss and cuddle, making him cry and generally frustrating Mummy and Daddy. However, (and I probably shouldn't say this incase it causes a jinx) when I am on my own, like tonight, both are really well behaved. There was no silliness, Carys even suggested that we read one of William's stories instaed of hers.

So can anyone tell me why bedtime can be hell on wheels when there is one adult to each child?