Can Moons Have Moons?

Yes, in theory, moons can have moons. The region of space around a satellite where a sub-satellite

sub-satellite

A subsatellite, also known as a submoon, or moonmoon, is a "moon of a moon" or a hypothetical natural satellite that orbits the moon of a planet. It is inferred from the empirical study of natural satellites in the Solar System that subsatellites may be rare, albeit possible, elements of planetary systems.

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can exist is called the Hill sphere. Outside the Hill sphere, a sub-satellite would be lost from its orbit about the satellite. An easy example is the Sun-Earth-Moon system.

Do any moon have moons?

In the Solar System, we have the central Sun, a great many planets, asteroids, Kuiper belt objects, and moons. While most of the planets have moons, and some of the Kuiper belt objects and even asteroids have natural satellites that orbit them, there are no known "moons of moons" out there.

Can a moon have moons of its own?

Yes, it is possible for a moon to itself have moons and/or rings, and there are a few places where scientists have suggested that this is (or was) the case. However, moons tend to rotate slowly, and this makes it difficult for a moon's moon to find a stable orbit.