Tracing the Family line

I and my cousin Sarah were tracing the family line, we're a large family. But there was a story that the family line nearly ended 2 hundred years ago. So we started looking and sure enough, all lines met at one person. At first, we thought he had married 6 times and 5 had passed away due to childbirth or something else. But as we checked each wife they had several children to him at the same time and all outlived him. 27 children in all and on further checking all the wives were related to each other mothers and their daughters. The 2 mothers were sisters and widows, 1 with 3 daughters and the other 1 daughter. There was no incest involved, as our great great great great great grandfather was no relation to them. As the last in a noble line, he wanted to ensure the family line. Marrying 1 woman wouldn't be a guarantee of its future. But being the last living male and having 6 different titles. He married a woman under a different title and so their babies were legal heirs and all records were only kept at the church where the wedding had taken place. The wives all knew and kept the secret. With 16 boys the family line was secured.