I have twin boys who've just turned 4. DTS2 is NT and seems to be 'normal' for his age - occasional tantrums but on the whole plays well with other DC, eats well, sleeps well.
DTS1 has always been more 'highly strung' and now they've started school (mornings only) is having absolute meltdowns from tiredness. The red mist descends and that's it, he will shout/ hit/ throw things until he calms down. He just doesn't seem to be able to control his impulses and will still lash out at other DC occasionally (mortifying) and scratch family members (very annoying), even though he's been told time and time again that it's naughty, to use his kind hands etc. Nothing gets through to him when he's in a temper.
He's always been a fussy eater and not a great sleeper, plus he mouth breathes and is constantly overtired. He's on the waiting list to have adenoids & tonsils removed and grommets fitted as his hearing is poor too, but I don't know if I'm pinning my hopes on it as a miracle cure?! Should I investigate any ADD help in the area too? I'm just so worried that DTS2 will leave him behind socially and no-one will want to play with him because he's the kid that hits 
90% of the time he is a lovely, kind, sweet little boy who will happily help me and talk to me. But when he's tired then this behaviour really comes to the fore. The DTs have always fought like cat and dog but DTS2 seems to know that he shouldn't extend this to other DC, DTS1 doesn't.
If anyone has any suggestions to help then they would be most gratefully received. It breaks my heart to think of him losing friends over this, but it's too difficult for me to arrange playdates for him when he might hurt other DC.