They say...

Opposites attract.

Well, maybe they weren't talking about twins, but growing in the same uterus is about as close as two opposites can get.
Even now, on the "outside" - 3+ years later, they're super close...BUT, they're also super opposite.

 and as more evidence a fun look at a FB post from April 15:
I took a half hour to "ignore" (if thats possible) my troops while I watched the Duggars.
2 potty accidents.
One twin stood still screaming in his wet clothes glued to his spot.
The other changed clothes and started a small load of laundry. (Sure it was dirty stuff in the dryer...but he deserves some props.)
....Guess who did which.

I love that they're opposites!
Their interests actually rarely cross.
Which makes me hope that they won't be fighting over girlfriends when that day comes (you know - in like 20 years...) ;)