The Dutch were slow to adopt surnames - especially in the upper Groningen province from where the Kruizenga family derives.  The Dutch naming tradition passed the name of the father to each child as a sort of surname.  Thus we see the children of Derk Jacobs all bearing the "middle" name of "Derks".

There was a strict naming tradition that was in place until the recent century.  There are certainly exceptions - but these were the rules.

Naming Conventions - Sons

1. named after Father's Father
2. named after Mother's Father
3. named after Father's Paternal Grandfather
4. named after Mother's Paternal Grandfather
5. named after Father's Maternal Grandfather
6. named after Mother's Maternal Grandfather

Naming Conventions - Daughters

1. named after Mother's Mother
2. named after Father's Mother
3. named after Mother's Maternal Grandmother
4. named after Father's Maternal Grandmother
5. named after Mother's Paternal Grandmother
6. named after Father's Paternal Grandmother

If a male child was not available to name after a grandfather, it is often common to see a daughter given a feminized version of the grandfather's name.  This can be done by adding the suffix je(n), ke(n), pje(n), tge(n), tghe(n), tie(n), tije(n), tje(n), or tke(n).

Gerritje for Gerrit.  Jantje for Jan.

Also, because the infant mortality rate was so high, it is not uncommon to see the same name given succeeding infants in the same family.