I came across your post from 2001. By now you probably have the info on family Baar and Swierenga that you were seeking?
Derk Baar is a brother to my Great Grandfather Simen Baar who emigrated to the U.S. in 1870 and settled in Chicago as did Derk. So I have a lot of info on the Baar tree from the Netherlands.
Diena Swierenga could be related to my wife. Her maternal family includes Henrietta Swierenga-Dykhius married to Ralph Dykhuis. They lived in Chicago as well.
I would love to share info on both families with you if you would like.