I have looked over the Clare Library materials pretty thoroughly by now. Not that, I am sure, I haven't missed a lot of points, because there is a great lot in there. But I had noticed that, at the time My great-grandfather Mathias lived in Clare (b. 1833 until emigrated 1851), there were a lot of Breens in Clare! Somewhere I believe I read that the name was derived from O'Brien. Also, I believe I read that the O'Briens were one of the old families of Clare, so perhaps that explains why there are a lot of them in the mid-1800s. It is interesting to note that the, very likely, same Thomas in Lakyle, Kilofin is entered as Thomas Breen in the 1838 Tithe Applotment and as Thomas Brien in the 1855 Griffith's Valuation. I am virtually certain this must be the same person, and that it is the father of "my" Mathias, since his biography of 1890 says that his father stayed on his farm in Ireland (at "Laghkil" which is almost touching Ballina) when Mathias and his sister emigrated in 1851 and did not die until about 1888. I have noted the Breens also at Labasheeda in Kilofin.
I think it is possible that all these folks were related, perhaps not closely. I'm fairly certain my immediate ancestors are the 3 Breens of Ballina/Lakyle (Mathias the senior, Thomas and Mathias) in Kilofin.
It is also interesting that the 1901 and 1911 Census both show Breens still living at Lakyle. I am wondering if Thomas had another wife and son after Mathias and Margaret left in 1851? The only way I am going to possibly solve this would seem to be parish church records, which are probably not acessible to me in the States (possibly on microfilm through the Mormon organizations).
I'm very interested to hear more of your Breens if you think there is a link of your Michael, buried in Kilmacduane, to my Breen's in Kilofin. Thank you for your interest.