If you are related to your mother and your father, you too are a victim of pedigree collapse. Pedigree collapse is a basic principle of ancestry. The definition of this condition is a little complex. Essentially, some of your ancestors married their own relatives. As you go back in time, this intermarriage becomes more and more prevalent. The effect of the intermarriage is that the number of your ancestors does not actually increase in a regular geometric progression (i.e. 2, 4, 8, 16, etc.), but instead, at some point in the past, the numbers actually begin to decrease dramatically. If you were to view your pedigree in a diagram, the resultant image would look similar to a snake that had swallowed a mouse whole. The number of persons in your family lines would increase to a point in time and then begin to decrease.
If the geometric progression of your ancestors was a reality, in about 30 generations, you would have more theoretical ancestors than the entire population of the world. In my own case, this phenomena began with my own parents, who were 2nd cousins, that is, they shared the same great-grandparents. Another obvious fact is that the smaller the ancestral community, the more likely it will be that your ancestors married their own cousins. Pedigree collapse is more common among populations where transportation was limited or in small isolated populations, such as islands.
If you want and current graphic example of pedigree collapse, you can enter your ancestry into the FamilySearch.org Family Tree program and then use the Relative Finder app to see all your relatives. You may find out that you are related to your spouse.