Boys in disadvantaged circumstances—not just girls from wealthy backgrounds—are at increased risk of disordered eating, research finds.

In a study of identical twins, the sibling who exercised more had lower signs of metabolic disease, researchers found.

New findings about the cause of multiple sclerosis come from a study of 61 sets of identical twins, one with MS and one without.

Gestures like waving and pointing go hand-in-hand with first words. A new study finds twins do both later than single-born children.

Harsh parenting practices like spanking, not genetics, are linked to higher levels of behavior problems in children, according to a new study with twins.

Twins show that genes play a significant role in how affectionate women are, but not guys. Plus, tips for how huggers can get through social distancing.

Families with multiple births face disadvantages "at every point of care in our healthcare system," a report finds.

Astronaut Scott Kelly spent 340 days in space. His twin brother, astronaut Mark Kelly, stayed on Earth. Here's how their mitochondria compare.