As far as Frank goes I can't help you, but I've had a similiar problem before.Depending on when the 1870 Census was recorded (in your case hopefully after May) you can run through the records until you find him and his parents.Alternatively you could use a state census since he might have been missed in 1870 (do to his birth date).Unfortunately you cant use the 1880 census as it was destroyed in a fire.
This is a time consuming task but it worked for me.In NY the early censuses are indexed you might be in luck and find the same for Wisc. and that would speed up the task.Of course you need to get a hold of the census for Wisc. too. Plan a vacation :)