I'm struggling to gain any traction on the McCabe side. The 1915 civil marriage registration indicated John James' birth c. 1890 and named his father as James McCabe, a policeman in the R.I.C. A transcript of the St. Malachy's church record of that same marriage added into the mix the name of his mother as Annie McKinstry. The relevant 1911 Ireland Census return showed Annie as a widow, born in Co. Antrim c. 1867 and married c. 1887, with all 3 children born in Belfast - c. 1894 (Kathleen), c. 1892 (John James) and c. 1890 (Mary).
I can't yet find a marriage for James McCabe (there is one of a so named policeman to an Anna Meek in St. Malachy's Belfast in 1886, but I can't see how it would fit). I can't yet find a 1901 Ireland Census return for the McCabes. I can't yet find births for John James or his sisters. So fresh eyes needed I think, in case I'm looking but just not seeing.