Very sorry to hear about your loss. I am a cat lover myself, in fact I just got back from the local cat protection society where I visited cats that need homes. It's upsetting to see that cats from my last visit (2-3 months ago) are still there, waiting for a home.
I hope your son can understand what has happened and in time overcome his grief, and remember the good times rather than be sad. It does sound like you have a big 'family' to help keep you going though!
