The proposed relationship of John Aloysius O'Brien as the father of Florence O'Brien and Cecelia Bernice Veronica O'Brien is supported by DNA evidence indicating shared ancestry within the family lines.

Specifically, DNA evidence confirms a 2nd cousin, once removed relationship between KLF (a descendant of the Florence O'Brien ancestral line) and LO (a descendant of the Cecelia Bernice Veronica O'Brien ancestral line) with a shared segment of 124.21 cM across 7 HIR segments.

This match is consistent with their placement within these shared ancestral branches.