Conversation with BR this morning on our way out of the house:
BR: "Lamb and Froggie and Giraffe are sitting together. They are sisters."
Me: "Sisters are nice."
BR: "Papa is a sister."
Me: "Well, no, not quite."
BR: "Papa is a brother."
Me: "Yes, he is."
BR: "Papa is a brother to Mummy?"
Of course I did go into the whole explanation of who is related to whom and how, but I thought it was just so cute to watch her explore all these new (to her) concepts...