I am wondering...
Are the younger kitties actual kittens?
Did these people educate themselves on what it's like to add kittens to an only older cat? Did they do a proper integration? And do they fully appreciate how lucky they are to have a 19 year old cat without a lot of difficult-to-manage health issues? I'm guessing it's a no to all but the first of these questions.

This families children definitely don't need to learn that just because something is old, it gets disposed of.

I know what it's like to have people as friends with pets which they don't treat properly, or at least properly in my opinion. Of the closest families to me either by friendship or blood relations, 5 have pets and only 1 of them treats their pets even close to what I think is right. It's hard to hold your tongue. You have to weigh: Is my friendship with these people worth letting our differences in what we do with pets slide? Or is the way I think pets should be treated strong enough to strain or end a friendship? I'm not confrontational enough to say a whole lot to our friends who, in my opinion, are lacking in their pet parenting....so I pretty much let the pet thing slide and keep our friendship going. It doesn't always sit well with me to be that way, but.....