Hope this helps. 
John Christian of William Christian & Ann Callow 28 Jul 1782 Ramsey
   “         “          “ John         “           “ Ann Christian 13 Jan 1782 Bride
   “           “        “ Edmond   “            “ Margaret Caghin  05 May 1782 Kirk Rushen
   “          “          “ James      “            “ Isabel Costain  13 Feb 1783 Kirk Rushen
   “           “         “ Charles    “             “ Kathne Mc Bryde 29 May 1783 Kirk Michael
    “         “         “ William Christian  “ Elizabeth Lace 21 Dec 1783 Kirk Andreas
  “           “         “William Christian   “ Isable Cowle 14 Mar 1874 Kirk Bride

You will find a lot of information about the Christian family on Frances Coakley’s site.
It is quite feasible that a Christian born in the Isle of Man would have many relatives in Waterford.
To quote from ‘Yesterdays behind the door’ by Mrs Hicks Beach. ‘When  George (son of William Christian. Illiam Dhone) died in 1694 his son William in 1700 sold Ronaldsway, and he bought the Old Grange, Waterford from the executors of his uncle Patricius who had settled in Ireland and had died in 1687 as Prebendary of Lismore Cathedral. Four generations of his descendants lived at Old Grange from 1700 onwards, and an enormous family tree, with an astounding superfluity of females, branches out.
(Patricius was Illiam Dhone’s  eighth son)