A new study suggests humans are predominantly monogamous, with approximately two-thirds of sibling pairs sharing both parents across 103 populations. Researchers compared human social structures to species like beavers and mole rats, noting that human multi-male, multi-female group living differs from solitary pairs or colony-like structures. The findings, which analyze family records and archaeological data, offer scientific support for concepts of natural fidelity and romantic idealism, indicating humans have been monogamous across time and space.