Stars may all be born in pairs and lose their siblings later
... with regard to mass, meaning that some former companions could be brown dwarfs cast out by larger stars. The authors of the paper, accepted in the Monthly Notices of the Royal Astronomical Society, say more work is needed to confirm their hypothesis.
Astronomers Discover That Our Sun Likely Had an “Evil” Twin That Killed the Dinosaurs
The Sun Probably Lost a Binary Twin Billions of Years Ago
Astronomical Twins: Lonely Sun May Have Had A Pair