2 yrs. After a colonoscopy I had another and they found a large polyp in the colon is that unusual? I have colon cancer in my family is that a concern

Not unusual. . Colon polyps recur or you grow new ones. This is why it is important to have regular colonoscopies, especially with your personal and family history.
Yes. Developing a new polyp may not be unusual , if you have a family history ( blood relatives ) of several members has colon cancer , is a concern , need genetic counseling and genetic study .Discuss with your doctor , will get best advice.