Jupiter has moons almost as big as Earth. It is possible, but not likely, that these close-in giant gas planets around other stars could have a "moon" that has life on it since the temperature itself may be OK.
Either that or our ability to detect gravitational influences of smaller planets like Earth and Mars inside what we believe to be the "living zone" of their stars isn't well enough developed yet....
Detecting the gravitational distortions of a gas giant close to a star is easier than detecting them from a much much smaller planet further away from the star.
Time will tell eventually.
Juptier's moons are much smaller than Earth. The largest ones have a diameter around 1/8 that of Earth, meaning they are 1/512 the size of Earth.