My DS (6) is always quite grumpy about my DMIL and DFIL visiting, and after giving them a usually fairly lukewarm reception if they do anything to annoy him he says mean things in an outburst like 'I hate you' and 'go home'. They are understandably sensitive about such comments and are usually upset and go in another room and read a book etc and stop interacting with us. I obviously make him apologise but he's not really sorry and it's really awkward. When they visit it's more of a cup of tea and chatting with us adults than playing with the children, so maybe he resents them taking up our attention. I've tried to encourage them to play with him etc but it doesn't come naturally to them and it's hard to force. Any suggestions?