Researching the entire family is advised, but we don’t always do it.
I was trying to pin down information on an aunt, Wilhelmina (Trautvetter) Senf Kraft–particularly when she managed to settle in Illinois. It was not until I obtained the christening record of each of her grandchildren that I was able to do that.
There as one of the sponsors for one of her grandchildren was Wilhelmina. It helped me to pinpoint when she had arrived in Illinois.