Here's a few: magnesium, oxygen, silicon, phosphate, and aluminum are all found in earth's crust in high proportion. oxygen being the highest proportion of any other element.
Natural barriers include the skin, mucous membranes, tears, earwax, mucus, and stomach acid. Also, the normal flow of urine washes out microorganisms that enter the urinary tract. The immune system uses white blood cells and antibodies to identify and eliminate organisms that get through the body's natural barriers.
both having gravity, you can touch and see both of it. It also possible if microorganisms can live on both of them.
They both have shape also.
They would not have food and/or mates
