No one in my family history going back several generations had colo/rectal cancer. Yet I developed it at age 41. Diet is increasingly viewed as a factor.
I had it at 26, go figure. My petvtheory is that in orser to get the average age back to 50, you need someone like me for every 80 year old, statistics are a bitch. That also means my children will have screening coloscopies starting age 16.
Have you got your genes tested? People can have Lynch syndrome and not develop cancer. Colon cancer is also a silent danger in that it can grow for years without any noticeable symptoms.
I got colon cancer at age 35 (despite being a vegetarian, BTW), and it was first then that suspicion was raised that there could be a hereditary component - which was later confirmed by a gene test.