After looking at the dates, I wonder if the two families are connected but perhaps not immediately. From what I have seen in the past, Randall, Rebecca, Charles, Alexander, and Sally were the only children of Randal and Rebecca. As you have mentioned, it seems they must have moved to Digby at some point, as the names line up perfectly. I have never seen Donald and Elizabeth's names come up with Randal's but maybe there is some relation there. I will do some more looking and see if I can find more information.