I have an odd fear of getting appendicitis due to two cousins and a grandfather having it. do most people not get it? is it as common as tonsillitis?

Most people don't: get appendicitis. The annual incidence is about 10 cases per 100,000 population.

Appendicitis: Hi, Lifetime risk for Acute Appendicitis is 8.6% in men and 6.7% for women, so as u see the risk is not that high, also instead of focusing on something that it might not happen focus on positive things, being anxious about Appendicitis is not going to make its possibility any less. Good luck.

Not as common.: Appendicitis is not nearly as common as tonsillitis. It is not hereditary either. It is good that you know what it is, so you will be watchful if you have symptoms. But there is nothing you can do to prevent it, so why worry needlessly? It is very treatable, not like a bunch of other diseases! See http://en.wikipedia.org/wiki/Appendicitis