Family Meeting! What? - XSIL and XMIL together over a coffee - gasping, puffing and generally tutting over your letter, bewailing their lot and wondering how such jolly nice and decent folk like they believe they are could be so maligned!
Fantastic!
Oooh - wonder what the verdict will be! I know, I know! They'll reach the conclusion that on the whole their presents were pants, that they should be more caring over this sweet offspring of their son/brother and decide to call and wholeheartedly and unreservedly apologise.
Do let me know if I am right won't you!