Your GSs are not unique, Granny11i. I don't live close enough to care for mine (now 9 and 11) but a weekend visit can be quite wearing at times. There's a lot of winding up and retaliation going on and too often it gets physical. The younger one is a big lad, catching his brother up in height and exceeding him in weight. So it's by no means an unequal contest. Luckily the younger now has the tactic of retreating to his bedroom to read or play on his iPad. When they are doing things like playing tennis or kayaking, they are fine. I am glad they aren't able to come to my too-small house. At least in their house they can be separated and each has his own domain. There is no rule that says that brothers should be close. My two DSs get on well enough but don't have very much in common.