The first thing you should do is write down the Wiki ID # for both. (Sargent-xxx). Write down the mother of Samuel Jr. as well if that is wrong too.
Go to the page for the son and click on edit. On the right side of the page, just under the father's name is a link to remove or replace his father.
Pick the "replace" option at the top and enter the Wiki ID for Samuel Sr. Do the same for the mother if necessary.