I believe extended family is not necessarily blood related.   Recently, I came upon this site, looking for my friend "SCHIZZ" and instantly I was reading a post by him and a response by his friend "Chopper".  It reminded me of my brother and his friend.  T.D as I'll call him, became my brother's friend in second grade and since my brother didn't have a brother,just sisters, well he became another brother to the all of us.  T.D spent a great deal of time at our house especially on the days when my mother would fix chili for supper, or apple pie for desert.  He would fly over on his bicycle or in his Toyota truck to make sure he got his lion's share of the goodies.
During my childhood, I can remember  "The Odie brothers" as they liked to call themselves after Garfield's sidekick, going out to the garage and modifying their mountain bikes in all sorts of designs, from new colors to " mud-slicker"tires.  This ceremony was usually topped off by a spin in the driveway  and jumping homemade ramps in all sorts of heights and lengths.
I can say that I wasn't innocent of this adventure because some days I would join them on my bicycle.
During one winter, I remember them taking their bikes out to The Alum Creek Park, in Delaware County, Ohio and racing them down the snow covered dam.  At the house it was a different sight, two boys taking their bikes and jumping the ditch with an occasional miss and impaling the front wheel causing them to fall off with a burst of snow.  My dad would look at them and call them a couple of yo-yo's.
Even as young adults, things didn't change, I was regaled of stories of them driving backwards with my dad's old GMC truck through McDonald's Drive-Thu just to see the reaction of the lady at the window.
It's fun to have someone you can be silly with, even as adults we can laugh at those crazy experiences. I had always heard that laughter is the best medicine.  So here's to the "Best Of Friends" be sister or brother, it doesn't matter.