Should I make DS include his younger sister when he's playing with friends?

[wonderingwondering]

Not quite as black-and-white as the title suggests. But DS (5) has friends over to play, and of course DD (2) wants to join in. The rule I imposed is if they are in the (downstairs) playroom, they have to include her, and if they want to play without her, they go to his bedroom.

That seemed to work, until DS and his friends started calling DD upstairs and then hiding from her (hide-and-seek, apparently....), and when I set DD up to play on her own, DS then wanted to play with what she was playing with....

Any tips on how to handle this? His main friends don't have little brothers/sisters, and anyway, he's now at an age where he ought to be able to have his friends round for more independent play-dates, rather than the mum and any siblings always staying too.

Either play or don't play - don't tease. He's being spiteful, although he probably won't see it that way. Tell him if he calls her upstairs he must let her join in everything or his friend has to go home.

You shouldn't make him play with her, but you should get him to stop teasing her, and demanding to be involved in her things if he won't let her be involved in his!

Well, Mrs Wobble, I did explain that to him [in one ear and out the other]! But I feel like I spend the whole time pulling him to one side. Perhaps he just needs to learn. I was quite cross about the teasing, and have spoken to him about it before his friend arrived. Bit he gets so whipped up.