Helena’s father, Dennis Benjamin Killeen (1829-1914) was married to Ellen O’Brien.
It’s through Dennis Benjamin that we’ve been able to trace the family back to Ireland.
His father Denis Killeen is mentioned in a history of Ottawa published in 1927 [A.H.D. Ross, Ottawa: Past and Present (Ottawa: Thorborn & Abbott, 1927), p. 39]:
“the first white child born in the Township of March was Patrick Killean, whose father, Denis Killean, was in Captain Monk’s employ, and the second was Benning Monk.”
An earlier mention of the same information came in a talk by Mrs. M.H. Ahearn, “The Settlers of March Township,” which was first read before the Women’s Canadian Historical Society of Ottawa on 10 March 1899, and later published by the Ontario Historical Society [Mrs. M.H. Ahearn, "The Settlers of March Township," Ontario Historical Society, Papers and Records, vol. 3 (Toronto: 1901; reprint, Millwood, New York: Kraus Reprint Co., 1975), pp. 98-99].
Denis, born around 1786 in the parish of Meelick in East County Galway, Ireland, had served under Captain John Benning Monk in the 97th Regiment of Foot. He had apparently then followed Monk to March township as some sort of domestic (or “soldier servant,” in Mrs. Ahearn’s words). He later received a patent from the Crown, in 1828, for 100 acres at Concession 3, Lot 11, March township.
Thanks to Mary Catherine Moran for these details from her website Ottawa Valley Irish.