The Moon which also shares a mysterious link with it's larger sibling Earth.
After reading about The Mysterious Link Between Twins, I felt compelled to share the story about my own grandfather and his brother that also happened to be twins.
My grandfather and my grand-uncle did share a special link and also worked for years in the field of ghost hunting. Both of them had special abilities that helped them, while my Grandfather was claircognizant and had a instinctive ability to seemingly know what and how to take care of the spirit entities or haunting in question, his brother was clairvoyant and could see them, he described them to sometime seem quite opaque and other times almost as solid as you and I, especially if it happened to be a angered spirit.
Naturally the twins would be called on to take care of hauntings, and help lost family members spirits find their peace, lost spirits that was very common because there was so many that would get lost at sea in the harsh Nordic Sea, which also gave the life blood to the people of Northern Norway.
Like explained in The Mysterious Link Between Twin, my grandfather and his brother also shared a mysterious link, that seemed to make them able to seemingly communicate without use of words, and even when apart they would know what state the other one was in. Like when my grand-uncle passed away my grandfather immediately knew he had passed over.