The Chinese give a beautiful explanation to this. The thumb represents your parents. The index finger represents your siblings. The middle finger represents yourself. The ring finger represents your life partner. The little finger/pinky represents your children. Hold your hands together like the picture. Join your middle fingers back-to-back, and the remaining fingers tip-to-tip. Now, try to separate your thumbs. They will separate because your parents are not destined to live with you forever.