People are dicks. Point out their bickering kids and compare it to your lovely calm home. Point out that you can afford to go on holiday when they can't. If you're really on a roll talk about how you will be to be able to leave a whole house to your child in their inheritance, rather than having to split it.
If those things don't work, thump 'em in the chops.
And definitely call them out on it, nosey shites.