Yes, I too have discovered some of my Ancestors beeing slave owners and a couple had children with them. In my case they did recognize the children and included them in wills. In FamilySearch.org under the Catholic section there are books with just the slaves under San Juan. Unfortunately they did not give last names in a lot of them so you have to sit and read thru when you find the First name. EX. Jose ( which are thousands) you will need to read and hope you get lucky that they wrote in the owners. I have been lucky in some. It is a shame that back then they would not post their last names. I can tell you that the surname Ramirez de Arellano was a BIG owner as some where Judges, Priests, high Business people and very wealthy people and GOOD owners as far as I can tell. I have that surname in my line. As far as the Move you may have to check your dates between your Ancestors move and the Civil War. Civil war was between 1861-1865 in Sumter South Carolina so check what may have driven them to make the move. Slavery in Puerto Rico was Abolished in 1873. Google it up and you will find LOTS of links to Puerto Rico slavery. Hope this helps.