rough play with sister

Question
I have a 9 1/2 week old puppy; my parents have his sister.  We purchased
them at the same time --two weeks ago, and they have been together most
of the time since.  Is it ok/normal for them to play really rough together?  
They constantly chase, nip, growl tackle and climb on each other.  Should this
be play be limited by separating them?  Also, my puppy seems pretty
disinterested in treats.  What should I be offering as a treat/reward?

Answer
Yes, it's pretty normal for them to play rough.  You do have to supervise playtime though because they're like human toddlers in the sense that it's all fun and glee then suddenly someone is crying because it got out of hand.  When it does - clap your hands and say NO then separate them for a few minutes.

Now, more important than treats is what you're feeding them.  For the next few months they're in a massive growth spurt and especially need a premium food.  I highly recommend Canidae (canned) for cockers.
If you go to Canidae.com you can find a store near you.  Use little or no kibble.

For treats I love Zukes or Solid Gold and they'd probably be sold at the same store that carries Canidae.  Unlike the supermarket treats (which are junk food) these are actually good for them.

Canidae has 3 formulas...use them all in rotation.  Puppies need feeding 4 to 5 times a day.  Take them out after every meal and every nap and basically every two hours.  Choose a command "go potty" or whatever you like and give that command when they go - then praise & reward.
Delores