Beware the second wife! It is easy to spot a second wife providing they have a different given name. Some men, inconsiderately to future genealogists, marry a second wife with the same first name. You can sense it is a different person if they are born in a different year or place though. Don't assume it is a mistake.
However yesterday I came across a man who married 2 women called Mary Sinclair. This only became clear on his death certificate where his son helpfully noted that they were cousins. The child I had attributed to Mary no 1 was in fact the child of Mary no 2!