If you plot the radii of the satellites of Saturn, Uranus and Neptune vs the orbit sizes you get a smooth concave curve, but not for Jupiter. This is probably very much like Bode's Law for the planets in the solar system. It all depends on the specific circumstances of the accretion disk that orbited the planet, and out of which the satellites formed. Many of the satellites of Saturn and Jupiter have been captured and are not natives.
Nature is full of interesting correlations.
We do not know why some of them exist. The radius-orbit relationship may be one of these. Return to the Ask the Space Scientist main page.