A group of comets which possess similar orbital characteristics, either because of a common origin or as a result of planetary perturbations. Members of some families, for example the Jupiter-family comets, do not have a common origin, and may have been captured from a wide range of original orbits. It was once believed that the gravitational influences of Saturn, Uranus, and Neptune also produced comet families, but the apparent association of comets with these planets is now thought to result from resonances with Jupiter’s orbital period. Halley-family comets are thought to have originated in the inner part of the Oort cloud. Other families, for example the Kreutz sungrazers, clearly have a common origin from the break-up of a precursor body.