Honor your sibling on Siblings Day, an unofficial holiday celebrated annually on April 10.

The unofficial day was created by New Yorker Claudia Evart in memory of her brother and sister, whom she lost early in her life.

Since 1998, US President Bill Clinton and governors of 39 states in the U.S. have officially recognized Siblings Day as an observance.

https://www.timeanddate.com/holidays/fun/siblings-day