Were President Franklin Roosevelt and President Theodore Roosevelt related?
Yes, these two presidents were related, though the relationship was not a very close one. Franklin Roosevelt was the 5th cousin of Theodore Roosevelt. Interestingly enough, Franklin Roosevelt was also a 5th cousin of the woman he married, Anna Eleanor Roosevelt (whose maiden name was Roosevelt).
This is not a very close family relationship. The last ancestor that Theodore Roosevelt and Franklin Roosevelt had in common was a man who lived from 1658 to 1742. His name was Nicholas Roosevelt.
As you can see, the relationship between the two presidents was not a close blood relationship. They were each born more than 100 years after the death of their common ancestor.