Coincidence or heriditary genes

A whole set of coincidences, some of which may be explained by hereditary, concerns my paternity. At the age of 48 I discovered that the man named on my birth certificate as my father was incorrect but I finally tracked down my biological father who we shall call Fred. By this time Fred had died but I contacted his remaining family which by this time was just a half-brother, David, and his family, two other siblings having died several years previously. Apart from the obvious family likeness there were so many other coincidences. I had been at school with David’s wife. My husband had been at school with David. David’s eldest son was called Matthew - as was our son, (when they sign Christmas cards you could hardly distinguish one signature from another). David had another son (sadly killed in a road accident) who was at the same school as our son Matthew. Our daughter has a gap in her front teeth as did my other half-brother who has died. David’s eldest son is an accountant as is our daughter. My half-sister, since deceased, was called Margaret – my middle name. But the greatest coincidence is that our son is a police officer, and was before I found this secret family, as was my biological father Fred. Further investigations show that there were many police officers on this side of the family, going back almost to the birth of the modern police force.