two sister pups

Question
I have got two 10 week old bordercollie x kelpie sisters. Everybody keeps telling me that I was daft for getting two sisters over a brother and sister. Is it true that they will be more aggresive towards eachother? Is there a way to curb any behaviours now rather than later?

Answer
Occasionally a couple of dogs will each have such a drive for dominance they can't be kept together.  It is most common with 2 females, so you did take a little extra risk with the females.  Just how much, I can't say.  Usually it isn't a problem.  

Get them spayed by 6 months, and give them strong leadership.  The key to most behavior problems is approaching things using the dog's natural instincts. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/ For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm