Siblings Day is a holiday recognized annually in some parts of the United States and Canada on April 10, and as Brothers Day and Sisters Day on May 31st in Europe, honoring the relationships of siblings. Unlike Mother's Day and Father's Day, it is not federally recognized in the United States, though the Siblings Day Foundation is working to change this. Since 1998, the governors of 49 states have officially issued proclamations to recognize Siblings Day in their state.
National Siblings Day, 10 April/Annual Celebration
National Siblings Day (10 April): Annual Celebration
Siblings Days are celebrated also in the United Kingdom, and India. The Hindu holiday of Raksha Bandhan Day also celebrates the bond of brothers and sisters.
The US holiday was conceived by Claudia Evart to honor the memory of her brother and sister who died at early ages. The Siblings Day Foundation was incorporated in 1997 and achieved non-profit status in 1999. Carolyn Maloney, then the U.S. Representative for New York's 14th congressional district, officially saluted the holiday and introduced it into the official Congressional Record of the United States Congress on April 10, 1997; and in subsequent years 2001, 2005 and 2008.
In the United States, approximately 80% of people have siblings. The holiday is intended to be a celebration of the relationship of brothers and sisters.
Source: wikipedia