Could just be a coincidence, I agree
there was a marriage between Ellen Leary and John Harrington at All Saints Fulham on 22 Nov 1829, witnesses Patrick Harrington and Mary Fleming. Bride, groom and witnesses all made their mark.
Has anyone found birth regs of John and James.
With such a big age gap, there is a possibility that John snr was widowed and remarried so Ellen not their mother.