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.
a monarch; a king, queen, or other supreme ruler. a person who has supreme power or authority. a group or body of persons or a state having sovereign authority. a gold coin of the United Kingdom, equal to one pound sterling: went out of circulation after 1914.