I have just recently learned that I have a thymoma and my former husband had one 8 years ago? Seem strange? I thought that this was rare? Does it seem strange that we both would have one.

Unusual. As dr. Stegman notes, it is an unusual coincidence. I concur, if not done already, you should consult with a skilled thoracic surgeon to assess best surgical approach. The majority of thymomas can be removed/resected using minimally invasive techniques such as vats or robotic.
I . I presume you already had surgery and hope you are doing well. You are correct that thymomas are very rare tumors with only about 500 diagnosed every year in the us. There are no known environmental or viral causes that would have put both you and your husband at risk for this type of tumor.