They're not.
all planets.
Mercury doesn't "have planets".
yes there is 2 planets but there are also dwarf ones too.
Do all planets and satellites lie on the same gravitational layer?
Mars, Uranus, and Venus are the planets with four letters in their names.
Planetesimals.
No two planets share the same moon.
They're not.
all planets.
they are the same
The planets of our solar system are most definitely NOT all the same size.
* saturn * uranus
Mercury doesn't "have planets".
there are no inner gas planets only outer gas planets but they are the same because they all have rings, they are all made of gas.
yes there is 2 planets but there are also dwarf ones too.
Because their distances are not the same from the Sun. Minus this factor, it is impossible for any planets to orbit on the same orbitation.