He's 20yo and wanted a new piece of furniture now he's "entertaining" a longish term GF. (Not a bed if that's relevant).
I agreed to buy it (as it's for the house and something we've been meaning to get for ages) but we agreed he'd be here for the delivery. He works shifts so we arranged delivery for a day when he was starting after I'm home so we had it covered.
As I bought it, all the reminder texts came to me and I forwarded them to him.
I reminded him this afternoon (I know I shouldn't need to) that the space needs to be cleared for delivery tomorrow.
He response, no problem I'll do it later, but you do realise I'm working days tomorrow.
No DS, I didn't. We specifically arranged that day because you said you'd be in and if that's changed why haven't you said so when you got one of the numerous reminders?
Only I was properly screaming at him about how he'd have to find a way to solve this problem and I wasn't doing it for him, this is what being a grown up is about. All reasonable points but I was vile 
DS has solved it. He's done a nice favour for his brother in exchange for DS2 making himself available for the delivery. It was the way he first attempted to dump it at my door that made me see red.
So DS does need to step up and take responsibility, but my response was way OTT.
What can I do to manage these outbursts? It's always DS1 who rubs me up the wrong way like this and I can easily see a time when I've driven him away 