Garryowen Part II: Porter -
The ultimate betrayal came with Johnny O'Connell's sister marrying a Fitzgerald and buying out the family brewery.

At Milford, the seat of her son Connell Fitzgerald, Esq., in an advance age, Mrs. Fitzgerald, sister of the late John Connell, Esq. of this city, brewer.
[Deaths, Limerick Chronicle, 19/03/1836]

Wine & Spirit Merchants., Fitzgerald & Co. Garryowen Brewery.
[Slater's National Commercial Directory of Ireland, 1846]

On Saturday last, John Fitzgerald, Esq., T.C. proprietor of the Garryowen Brewery...
[Deaths, Limerick Chronicle, 11/4/1860]

...the old established one at Garryowen, of which “Johnny Connell”, celebrated in song, was the owner, and which now belongs to a lady of his family. (1866)
[Lenihan]

Mr. Fitzgerald served his time to the best brewer in London... (Garryowen Brewery, 1872)
[Keane, Limerick Breweries, The Old Limerick Journal, 1981]
Note: The 100th anniversary, the Fitzgerald's closed the doors for good in 1881. Cousin Daniel "The Liberator" O'Connell and old man Guinness did not play nice together.