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.
Definition of 'reign'. reign (reÉªn ) If you say, for example, that silence reigns in a place or confusion reigns in a situation, you mean that the place is silent or the situation is confused. Confusion reigned about how the debate would end. A relative calm reigned over the city.