I'm 14 years old with my own passport,would i be able to travel from Canada to the Netherlands and back?

If I am 14 years old, almost 15 in November would I be able to travel with my 9 year old sister from Canada to the Netherlands to visit my aunt, uncle and cousins? I would my age get in the way or would it be simple to go there and after a few weeks, take a plane back?

You shouldnt have any problem, you would most likely be considered an unacompanied minor and there would be additional fee's involved when you board the plane for you and your sister.

You should check with the aircraft company you plan to do the travel. Some require a written statement by the parents, authorizing the travel, some have even a certain age limit for unaccompanied travel.
Best thing would be, after having clearance from the aircraft company to still have a written statement by your parents, so you will not run into problems at customs being considered as runaways.