Is Homesickness a Genetic Condition?

I'm part of the third generation of homesick women in my family.

My grandmother left Italy at 18 to follow my grandfather to America. He had come  back to his village to find a wife, and she agreed, thinking that America wasn't much further than Rome and she would return home every year or so. Much to her surprise, the next time she went to Italy, she had four children in tow and another on the way. While she was teaching me to make sauce and eggplant Parmesan this week, I asked where she went on her honeymoon. It turns out that she and my grandfather cut the honeymoon short because she was so upset by their impending departure from home. She said, "I don't know where we went. I didn't see anything because I was crying all the time."

My mother only moved about two hours away from home, but to someone who lived in a house full of people and commuted to college, the distance was huge. Both of my parents (who grew up a mile apart from each other) are crushed that they can't be at every Sunday dinner, birthday party, and school play. They packed us in the car for every holiday to make the two-hour trek, and for many weekends as well. I'm not sure how they got the three of us in the station wagon along with all the presents from Santa without us figuring out Santa's identity, but they did. They constantly toy with the idea of moving back--they've actually been thinking about it since I was eight--but they still think doing so would "uproot" their three adult children who don't live at home. 

Then there's me. I went away to college, I went away to grad school, and I went away for a job. But it kills me each time. And even now, when I leave home to get back on the plane, train, or bus that will take me far away from the people I love, my parents say, "Are you sure you have to go back? You don't have to leave, you know. Wouldn't you rather stay here with us?" And each time I leave, for the first five minutes on the plane, train, or bus, I can't see anything because I'm crying the whole time.