Permit me a litte rant please...

[chocolatesaltyballs22]

...so that I don't explode at home!! Two stepsons have been with us for less than 24 hours - arrived at 5pm last night. In that time they have managed to generate an entire basket full of washing (not a small one) and drank most of the milk that I have in the house. Husband is blind to it so I have to instruct him to put the washing machine on while I hide in my office quietly seething. I mean how the fuck is it even possible to dirty that many clothes in less than 24 hours? AIBU to think they are saving this shit up for when the come to stay with us?!

You know your problem OP? Gin. Forget the wine, you should be on gin.

@chocolatesaltyballs22

They have been shown how to use the washing machine. Several times. But they'd rather let the washing fairy do it.

The washing fairy shouldn't be such a mug.

@FangsForTheMemory

You know your problem OP? Gin. Forget the wine, you should be on gin.

That could be a plan....

OP,

Make it crystal clear to your husband, his kids, his laundry.

I would not be doing that laundry.
I wouldn't be cooking either for a 12 year old who was so dragged up as to speak like that to me.

You are very foolish to be taking that shit (literally) and doing anything for them.

No need for any arguments, just don't do it.

I would be so busy visiting and meeting friends.

Leave him to bond with his boys.

He sounds like a shit husband and a shit father, that his sons are so dragged up.

Enjoy the vino, you deserve it.

They sound like normal kids to me. It's hardly crime of the century to fill up a laundry basket and use the milk - thoughtless perhaps, but that's all. And this is easily sorted. Get your dh to do one load of laundry, which can dry and leave the rest until a more convenient time and presumably you've texted him already to get more milk.
This is bugging you because they aren't your kids, so you don't have the natural inclination to overlook normal irritants, as you would be inclined to if they were your kids.
Normally I have a huge amount of sympathy for step mums because a lot of issues stem from the father's behaviour but I do find myself feeling sorry for these boys, whose very existence seems to piss you off.