Siblings — especially twins — sometimes share the strangest traits, like throwing a ball with their head or picking up keys and crayons with their toes. Researchers want to know what's up with that.

Twins appear to be unusually abundant in Nigeria's southwestern city of Igbo-Ora. For the past 12 years, the community has organized an annual festival to celebrate twins.

NPR's Scott Simon shares the story of twins born 15 minutes apart, one just before midnight on Dec. 31, 2021, and one just after, and what their birth years might mean in the future.