Sideline Sibling
A kid who attends their sibling's competitions
Example
Ugh, I’ve got to spend my whole Saturday at Mia’s soccer tournament again
Sideline sibling life. You bringing snacks or just suffering in silence this time?
Oh, I’m prepared. Got my headphones, a book, and enough goldfish crackers to last through double overtime
Respect. Sideline siblings deserve medals too
Take the pop culture acronym challenge
A sideline sibling is a brother or sister who regularly tags along to watch their sibling's sports games, even if they'd rather be doing anything else. These kids can be found sitting on bleachers with snacks, reading a book, or just zoning out. Some kids may also play with other sideline siblings or go on solo adventures at the nearby park while their guardians watch their sibling's game.
The phrase gained popularity in parenting blogs and youth sports communities in the late 2010s as a fun way to acknowledge the overlooked role of the "other sibling" on game day. The term captures the unique experience of growing up in a family where one child plays sports, and the other becomes their unofficial cheerleader (or reluctant spectator).
For example, sideline siblings are often younger kids dragged to practices and weekend tournaments (but older siblings can claim the title, too). Parents and coaches most often use the term (some kids may use it as well), often with affection and a hint of humor.