Hi Mark, Bernard Doonan's son William Charles Doonan was my gggrandfather, born in Cavan in 1831, married Kate Adam in Westport Mayo in 1862, he was a methodist minister and died in Belfast in 1891, though his father was born a catholic.
I know Bernard had a brother called Patrick. There is an obituary after William Charles Doonan died, that mentions that his father Bernard was one of three brothers who changed their religion. I don't know who the third brother was but William was a strong name in the family. What was his religion? Could he have been a third brother to Bernard and Patrick?
Andrea