They are both 5 and he came round to play last week. They were upstairs and I heard lots of lip smacking noises and when I went to investigate I found my DD lying on her bed with this boy lying right on top of her and they were cuddling and kissing on the lips. They had closed the curtains and turned off the lights. When they saw me they leapt apart like a couple of teenagers and looked quite embarrassed. I made light of it and they came downstairs and played.
He came round again at the weekend and when he had gone home DD said to me "He asked me to do that special kiss again mummy, and he showed me his willie" .
Now I'm really at a loss as to how to handle this. I've mentioned it to his mum and she found it quite amusing, but it worries me.
Any comments/suggestions/similar experiences very welcome.