Just that really. My boy twins are 2.5 and cannot be left alone, otherwise it's scratching, biting, hitting... if I supervise then I can at least catch them (hopefully) before they start, but it feels like I can't turn my back for 5 minutes!
I've spoken to my HV and our conclusion was that they're such different personalities that they wouldn't be together out of choice, hence they get on each other's nerves - when they get older they should grow out of the hitting etc but till then every day is a challenge and I can't relax around them. It's awful but sometimes I wish I didn't have two, then at least there'd be no squabbling 
DS1 is starting to wake up really early too (6am or before), which wakes up DS2, who wakes me up - so we are all cross, tired and grumpy. I've tried putting him back to bed with some milk but he just bounces around and shouts.
Any ideas gratefully received! They go to preschool two mornings a week which helps, but we can't afford more...