1. All the planets orbit the Sun in elliptical orbits

venus is retrogade or rotates backwards

1. Almost all (perhaps all if one excludes Pluto) orbit on the same plane.
2. They mostly all rotate in the same direction.
3. Most have moons.
4. They all contain mostly the same elements, except that the closer the planet is to the sun the less lighter matter they tend to have.
5. They are all planets and are in the solar system.