Hi Andy,
Welcome to RootsChat.
Is this correct?
Hugh (1870-) married a Mary E Evans (1874) from Llanddona ...
From what I've found it seems that Mary Ellen's surname is Williams?
A Mary Pritchard's birth was registered as 9 Jul 1901 at Llanddaniel-fab, the daughter of Hugh Pritchard and Mary Ellen Williams and an Elizabeth Pritchard was registered 18 Feb 1903 with the same details.
Mary Ellen Williams married Hugh Pritchard in a civil ceremony at Bangor (FreeBMD Dec 1900 11b 903) and Catherine Williams married Hugh Pritchard, again in a civil ceremony at Bangor in 1911 (Mar 11b 536).
If I'm correct her birth was registered as 2 May 1872 at Llanddona, the daughter of Owen Williams and Elizabeth (nee) Williams.
Other children of the same parents, all born Llanddona, were:
Catherine - 1 Apr 1866; Martha - 31 Oct 1878; Ann - 11 Feb 1864; Elizabeth - 9 Apr 1859; Hannah - 18 Jan 1876; Hugh - 8 Jun 1861; John - 13 Jan 1857; Owen - 21 Jul 1854; Robert - 7 Jul 1869.
There was a marriage 11 Nov 1851 at Llanddona Church between Owen Williams, full age, miller of Llanddona Mill, son of Owen Williams, miller and Elizabeth Williams, minor, of Llanddona Mill, dau. of Hugh Williams, farmer.
I can't help with the birth in Liverpool of Hugh Pritchard (Snr).