Thanks guys. At least I know that this is normal behaviour! Yes, Mooshie, it's SO much fun when they both do it in the car... not! We do say to Charlie, "Toby's just saying 'I'm tired, Mum' " or something like that when he's crying, and that sometimes works - sometimes we even get a giggle out of him. It's good to know that he'll probably just grow out of it, but I might try to find that book in the meantime, thanks Melinda.