First names can be amazingly effective clues in our search for ancestors. Many times in my surname searches, I would find a family tree that I would either reject immediately, or keep as a possible connection on the basis of the first names in the tree. I didn't realize then that I was doing this because of an instinctive recognition of the common first name patterns used by my ancestors prior to the 20th century. There were many variations to this pattern, but the clues for you are in the repitition of a name through generations.
First names can also be a source of confusion.
When tracing records, you may find your ancestors in the habit of giving the exact name of a previous child who died to a later child. Many times, when a spouse died and the survivor remarried, the first child of that remarriage would be named after the deceased spouse. A child could be named after a recently deceased relative. These are all clues for your search. Sometimes, you will find discrepencies on your records because of an ancestor going by their middle name, nickname, or an anglicized version of their first name after immigrating.