As I'm sure you know, "In Rhode Island, obtaining title by adverse possession requires actual, open, notorious, hostile, continuous, and exclusive use of property under a claim of right for at least a period of ten years. Corrigan v. Nanian, 950 A.2d 1179, 1179 (R.I.2008)" If they were not paying taxes on the property, it may be presumed that they knew you and the prior owners were paying taxes on the property. If they knowingly allowed their neighbors to pay taxes on the property, then you can argue they weren't "using" the property in an open, notorious, and hostile way under a claim of right, otherwise they would have told your neighbors, "Hey, stop paying taxes on my land." In other words, you can't adversely possess property if you knowingly allow your neighbor to pay taxes on it.