The simian crease is one of the listed signs in Down Syndrome which would imply there's some genetic factor at play. My eldest daughter has a simian crease on one hand and the other hand is 'normal'.
Sovereign definition, a monarch; a king, queen, or other supreme ruler. See more.
The definition of crown is to give someone power, or to place a ceremonial headdress on a person's head. When you recognize a new person as king, this is an example of when you crown him. a garland or wreath worn on the head as a sign of honor, victory, etc.