My 3xG Aunt Mary claims, on the 1911 census, to have had 20 children (this would be between 1871 and 1900) born alive, and 17 still living, but I've only been able to find 15 so far. These include one born two years before she married, and three or four (not quite sure yet) born to a third man after her husband ran off and married another woman bigamously. She eventually married this man (after her husband had died), and died in 1938, aged 85!!
Linda
Added at 13.25: I've just found another one, so that's 16. Four to go, if Mary was telling the truth!