Two is a good number, of kids. More than two, awesome...your a better woman than I am! However, we really thought for the longest that Princess would be the only royal child in our home. Until the Good Lord blessed us with Duchess.
Now my children have a best friend, their sister. Plus when something is broken, its more fun trying to figure out who did it, takes the boring out of disciplining your children, really.
There is nothing quite a sweet as that rare moment of happy joy that is two siblings sharing a moment not filled with hair pulling (what is it with girls and hair pulling?), name calling, tattling and property theft. It's just delicious.... In fact some of my very closest friends let me adore their children from afar, I've noticed that they too have seen that rare sight.... when their kids are buddies, sharers of a secret or just being freaking cute.
SuperMan and SpiderMan here are another such case. What adorable boys. I swear their mom keeps them so far away so I won't eat their cheeks. Although I bet she'd happily drop them off for a week at a girl's spa in Bermuda....don't get any ideas missy!
To further point out this rare occurance in nature, here are two sets of such sibblings. Mine in the middle and my dear friends on the outsides. These children can't be alone in a house for five minutes without an ambulance being called. Usually for one of the older children....the burnette in green and the boy are just dangerous people....the older two don't stand a chance! Yet here they are, happily sharing space with smiles, no pinching, biting, yelling or kicking. 
