- They are all brilliant mathematicians.
- Their research has helped establish the fundamentals of much of computer science.
- They were all born in 1903.
- All of the above.
I almost added Frank Ramsey, also born in 1903, to the list. Certainly Ramsey Theory has played a major role in theoretical computer science. But the popularity of Ramsey Theory is due more to Paul Erd�s than to Ramsey who was mostly a philosopher.