Occasionally you are lucky enough to stumble upon a history of one of your ancestors.
Ole and Mari Finnestad's 2nd and 3rd born sons, Bert and Rasmus Finnestad and their respective families had left Illinois and moved to Saskatchewan, Canada. (Rasmus had taken a detour to Iowa prior to moving to Canada.)
I came across this biography* of Rasmus' daughter Rose Clara and Bert's daughter, Charlotte Finnestad from a Canadian website, "www.ourroots.ca". When I initially had found out Rose and Charlotte had married the same person, I wasn't sure whether it was accurate, but these types of biographies are helpful in explaining why the cousins married the same person.
The original webpage can be found here.
These types of documents are very helpful in filling in the blanks when you are attempting to create the multiple branches of your family tree.
* As always, click on a document or photo to have it pop up. Use your mouse's menu to bring it up in a new tab and click a second time on the document to enlarge it