All these four persons have a commonality. However, in their childhoods, persons 1, 2 and 3 missed out on an event that person 4 did not miss out on.
What was that event (specific to their commonality)?
The four persons are:
John Byrom, 29 February 1692 - 26 September 1763
Gioachino Rossini, 29 February 1792 - 13 November 1868
Augusta Savage, February 29, 1892 - March 27, 1962
Sean Abbott, born 29 February 1992
They were all ...
... born on the leap day, 29 February eight years before the turn of a century.
The event they missed was ...
... their eighth birthday, because the years 1700, 1800 and 1900 were not leap years. The year 2000, however, was a leap year, so Sean Abbott got to celebrate his "proper" birthday on 29 Februrary.