What Is My Name?

I believe I am having an identity crisis. It seems I don't know my own name.
Well, I finally ordered my birth certificate so I can get a passport and go to visit my family across the sea. To my surprise, I found that either I have been spelling my middle name incorrectly for over 50 years, my mother changed her mind, or the courthouse made a mistake. Hmmm. The middle name on the certificate is not what my mother told me it was. I called the courthouse and learned that I can change my name to what my mother told me it was. It will only take six months. Oh, and it will cost me (of course!).
Now, here's an even more interesting piece of info. I talked to PJ today and told her my story. She was born seven months before me. Our mothers were raised as sisters. She said that she originally was given a particular middle name, but a few months later, her mother added a second middle name...the same one that is on my birth certificate. So, I have several questions.
1. Who had it first?
2. Did one of our mothers influence the other?
3. Did my mother decide, after we both had the same name with the same spelling, that she would change the spelling of mine to not look so obvious?
4. Is it all a coincidence? A mistake? Nothing at all?
5. Are PJ and I actually fraternal twins?
The answers to these questions and other mysteries may be forthcoming. Or, they may remain Family Secrets.