it is ganyme and callisto
Ganymede is the biggest moon in the solar system.
going by the magnitude scale, Callisto's the brightest. Io 5.5 Europa 5.7 Ganymede 5.1 Callisto 6.1
The neighboring moons of Callisto are Ganymede, Europa, and Ia.
Io Europa Ganymede Callisto
JUPITER
Orbiting planet Jupiter
From Brightest to Dimmest: Ganymede Io Europa Callisto Use JPL's HORIZONS web ephemeris to look up apparent magnitudes of jovian satellites.
Io, Europa, Ganymede and Callisto are the four satellites that orbit Jupiter.
Satelites of Jupiter
The four largest moons of Jupiter discovered by Galileo are Io, Europa, Ganymede, and Callisto.
Jupiter's two largest moons are Ganymede and Callisto. Ganymede is the largest moon in the solar system and is even bigger than the planet Mercury. Callisto is the second largest moon of Jupiter and is known for its heavily cratered surface.
Ganymede is the largest, then Callisto.