The Terrible Twos

We're currently having fun with the TERRIBLE TWOS in stereo.  I'd heard about 'the twos' from other parents but had no idea what it would be like.  Here's a brief rundown...

Mason's started to demand things such as "Daddy, go get my water!"  When we tell her to ask nicely she'll bark out "Daddy, PLEASE go get my water!"  She also went through a phase of hitting Jacob.  This has fortunately died down because it put us in a really difficult position - Mason would hit, or sometimes just tap Jacob and he'd start crying.  Now, should we tell him to hit back or not?  What would you do?

Jacob's recently become defiant.  He'll do something that he knows is wrong like throwing toys around or pulling on the curtains and then keep doing it even when, or should I say, especially when, we tell him not to.

I know this is just normal 2-year old behavior and they'll eventually grow out of it (with our help) but it's a little frustrating, particularly when they gang up on us!