Writing Exercise: Grandfather Squared

In our writing group we had a new exercise. Imagine you have discovered a letter inside a grandfather clock. The letter is from your grandfather and was written when you were born. Here is what I wrote:

Dear Grandchild,
  Now that you have joined us int he real world, I wanted you to know the truth about the family. We had a family meeting a couple of months back, and even though I am the patriarch, the decision was to not let you know the family history. We voted, but I'm old-fashioned enough to believe a family is not a democracy. So I've resorted to this tactic--placing the information in a safety deposit box to be opened on your fifteenth birthday. You'll be old enough to be responsible for yourself and rebellious enough to want to disbelieve all the hogwash the rest of the family has told you. I'm going to leave some money too, though what you'll be able to do with it in fifteen years is up to you.
  Today is two days after your birth. You've left the hospital and the prying eyes and probes and questions of the staff there. The secret is easy to hide who you can only see skin deep. Looking deeper into yourself is an important thing to do. Most people take that metaphorically, but in our case, it's important literally. The first signs of our difference are barely recognizable in the first few days of life, but things rapidly change in short order.
  I suppose you've guessed by now that there's something "unnatural" about you. Maybe you've felt that way for years. I'm writing to tell you that it certainly is not "unnatural," it is just unearthly.
  Yes, you may have figured it out by now. Our ancestors were immigrants to this land, but not from Europe or Asia or Africa or any other land on the globe. We are from another planet, far away from here.
  My grandfather (your great-great-grandfather) came in a ship across the galaxy and was marooned here on the Earth. Why isn't so important. How is...he was left behind by his comrades with no technology, so no way to call back home or build another ship or re-establish his old life. He was alone. The best his technical know-how could do at the time was build simple machines like watches. He got a job working for Edison but they had a falling out. Edison completely disowned my grandfather, taking credit for his inventions. Granddad move on to Tesla hoping to recreate enough technology to call for a ride back home. Tesla was also secretive and greedy, disowning dad.

That's as far as I got with the story. In case anyone thinks it's a mistake, I did intend for the grandchild to find the letter in the grandfather clock (so no money and no safety deposit box). I wasn't sure about the age of the discovery. Possibly the child is twelve or twenty-five or sixty-five. Anything but fifteen. The possibilities are good. Also, the gender of the child is unspecified. Our writing group has longer readings on the second meeting of the month, so I may expand on this for one of those sessions.