Earth is complex product. Tides, created by the Moon, are important to mix water and to clean coasts. Metal core of the Earth is producing magnetic shield. All that is created due to collision of Earth with large object, which is comparable to Earth, and capturing it.
It is unlikely, that our Galaxy will contain too many systems created by two objects with comparable mass, because such systems are unstable. We can calculate this number by comparing number of star systems with two comparable stars in the system to number of regular stars.
It is unlikely, that our Galaxy will contain too many systems created by two objects with comparable mass, because such systems are unstable. We can calculate this number by comparing number of star systems with two comparable stars in the system to number of regular stars.