Hayley and Lucy being entertained by Oliver.Lucy often just sits and watches Oliver. There's good chance this is partly down to self-preservation in case he absent-mindedly sits on her or rushes over and gives her an over-exhuberant hug. But sometimes it is just because she wants to know what he is doing and would probably join in herself, if only she could. In short, she has the advantage of a younger sibling: the older sibling is a free home entertainment system.
This morning Hayley was sitting at the dining table with Lucy on her knee. Oliver was sitting next to them on another chair. He started to bounce up and down in his seat. This made Lucy laugh. So Oliver did it more. This made Lucy laugh more, which in turn made made Oliver laugh... which made Lucy laugh more... which made Oliver bounce and laugh even more.... you get the picture.
It's probably the first time you could say that they have played and laughed together. Long may it continue.