And third cousins twice removed that you've never heard of...
I would imagine the pressure on a large prize lottery winner to donate to charities and every relative no matter how remote would be immense.
The first thing I would do is get new phone numbers and close any email accounts that I had, and then go into hiding for 3-6 months until the fever went down.
The next thing I would do is hire a lawyer, an accountant and an investment adviser to help me decide where and how to store the money.
I would put $50K into a basic checking account with a debit card for walking around money for the few months that I was underground. My only contact would would be with the lawyer and investment guy.
After the fever is gone and everyone else has moved on with their lives would I begin to remake contact with people.