There are two issues with your posting. The first is that you appear to believe that all people of the same surname (in this case Finley) are related. This in not case (even although our tourist board, for obvious commercial reasons, try to persuade people otherwise). Names evolved individually - and using the name Finley as an example, it derives from the Gaelic "fionn-laoch", meaning fair-haired warrior. It stands to reason therefore that there would have completely unrelated people throughout Scotland choosing this name as their own. The same applies to people who took occupational surnames such as Fisher. It would be folly to think that they are all descended from the same one fisherman. So don't assume that you're relaed to other Finley's, and don't assume that the owners of the castle are in any way related either, until such times as you are able to prove through documentation that they are.
Secondly, have you asked for proof from whoever has compiled your ancestral chart ? The nature of Scottish records is such that for the vast majority of families we are only able to prove back to around the mid-late 1700's. Otherwise you may find there has been a lot of guesswork involved. There are exceptions to this, especially if your family are from a priveleged background where multi-generation gravestones, wills, family documents etc may have survived the passage of time. However these are very much the exception rather than the rule.