Merging profiles means making 2 identical profiles into one.
I think what you are asking is how to connect them as father and son. If the sources support your assertion then all you need to do is go to the edit page of the father and look down the right hand side. There you will find add child, click, then add the profile number of the son, scroll down and click save.
However in this case it is pre-1700 and project protected, so you cannot proceed