What Is This Thing Called Love?

I've been wondering about love a lot lately. How to find it, how is feels, and my definition of it. I spent most of the Thanksgiving weekend watch my sister and her boyfriend play cute with each other. Tickles and kisses and attached hips. Most of all wondering what "I love you" means to my sister (as she said it a million times), and that made me wonder what the hell it means to me. I've never loved anyone the way someone loves their boyfriend or girlfriend. Do people even think about it? I don't think about loving my family and my close friends, that love just exists. It's there, I know it is. My mother, discussing my sister's affection for her boyfriend and how she treats him better than the family, said "it's different." How is it different? It's hard to say if I will ever know, I guess you can't know until you wake up one day and realize you're there.
But while I was home pondering the meaning of love (I hate that I used that phrase, but, oh well), I decided to busy myself by packing the remainder of my winter clothes to take with me back to Atlanta. Sifting through all the cardboard boxes sacked against my wall, I found one containing a present my father gave to me on my eighteenth birthday. Hidden in the dull beige pages of a Wendy's spiral notebook is the letter my father wrote to me the day I came into the world. I read it. Twice. I guess, that's what love is. So, for those of you who doubt that the emotion exists at times, the letter's below (errors and those parts unrelated to the subject). And for those of you who never doubted, I hope you never do.
If this is all the love I will ever know, I suppose it's more than I can ask for.

3-1-81
1:27 p.m.

Dear--
As I sit in the hospital watching your mother sleep have giving birth to what has to be the most beautiful baby ever I want to say a few things before time erodes them from my memory (your father has always been a bad speller).
Your mother is the only woman I could ever love. The hardships and pain she endured tonight only confirms to me her love and caring for you and for me. Never hurt her, her love for you from your first moment is clean and pure and truley unselfish. We will be the lucky ones knowing we are hers.
Your father, at two hours, is truly in love with you. We may question his abilities of fatherhood in the future but always remember I love you. You are the most beautiful girl I have ever seen. To see you come into this world from your mother's womb is my most cherished sight. From now forward I have two women in my life.
About your name; it has a special meaning to me. It is the title of a very old song which is now unknown . At a time in my life it was extremely important to me. To listen to the song, you wouldn't know how much strength it gave me. I love you, and to remember all these things, your mother and I named you this.
Your mother is still sleeping - but our tomorrows will only be better, since your arrival.
I love you now and always,
Father