I'm a cousin of Sadhbh Byrne and am therefore also descended from Arthur and Bridget Byrne of Ballymanus.
I found this connection several years ago but did not pursue it beyond the above generation (as you know it can be difficult to trace the surname Byrne in Wicklow).
Did you get a chance to look for a marriage record for Arthur and Bridget Byrne at all?
Assuming they were married in Killaveney it should be possible to find a marriage for them as the records for that parish go back to 1800. The records themselves are online but not indexed so a bit of patience could pay off. I'll see if I can find anything in my own documents on this also.
The marriage record should show which townsland the bride and groom were from so could be helpful for your research.