Most siblings born on the same day
Who
Cummins family
What
5 people
Where
United States (Clintwood)
When

The only verified example of a family producing five single children with coincident birthdays is that of Catherine (1952), Carol (1953), Charles (1956), Claudia (1961) and Cecilia (1966), born to Carolyn and Ralph Cummins (USA) all on 20 February.

The random odds against five single siblings sharing a birthdate are one in 17,797,577,730 - almost 4 times the world's population.