One of life’s great mysteries is how a father and mother can produce two children and have them be so different. I also wonder how some couples had a particular child and even wanted to chance having another like the first one, but that is a whole different story.

Each of you probably can think of examples of two siblings being as different as night and day. One is outgoing and funny, the other shy and serious. One is very athletic while their brother or sister is not. Same mother. Same father. Two total opposites. One is really charming and intelligent, the other a total ditz. O...