I know that george bush and his father were presidents, as well as John Adams (I think), is there any president of the USA who was biologically related to 2 or more other presidents?
Obviously at some level it's a degenerate question, because ultimately every human on earth is related.
So given that we are really good at genealogy these days, it probably shouldn't be surprising that there are oodles of them that we know of.
Looking over the link provided by Lars in the comments, it looks like the closest related triple were Madison, Polk, and Taylor who were second cousins (once removed in the case of Taylor and Polk).
Even Obama has known relation to three other presidents. James Madison was his third cousin9, LBJ his fourth3, and Carter his eighth2.
Going past that, frankly It would be much easier easier to list those who don't have two known relations. Those are (listed in order with presidency number):
- 1 Washington
- 3 Jefferson
- 5 Monroe*
- 7 Jackson
- 13 Filmore
- 15 Buchanan
- 17 A. Johnson
- 21 Arthur
- 28 Wilson
- 34 Eisenhower
- 35 Kennedy
- 36 LBJ*
- 40 Reagan
- 42 Clinton
You might notice that the pace slows down towards the end. That makes a certain amount of sense, as the genealogical fan-in increases as you move down generations.
Still, that's only 14 of the 45 Presidents.
* - Related to one other POTUS, but not two
Numeric Superscripts designate level of removal