have you really exhausted
http://www.rosdavies.com/SURNAMES/Mc/McGr.htm#graf who always needs donation for her unique co down website , her information is free except if used for profit I have placed some of her information for the McGRATTAN / McGRATTEN/ MEGRETTIN/ M'GRATTEN into a family tree format and add suggestions
Ros Davies has several entries for
a Hugh McGRATTAN might be father
residences Ballycran Ballygelagh [ Ardkeen parish]
starting with Gordon
under Gordon, Ann may have brothers etc perhaps
Hugh GORDON .Witter father of Michael bpt. 24 Jul 1853 at Ballygalget Catholic Church
James GORDON . Ballyphilip & Witter of Mount Ross; father of a child bpt. 18 Jul 1829 at Ballygalget Catholic Church PR
William GORDON . Witter father of Michael bpt. 12 Aug 1853 Ballygalget Catholic ChurchPR
William GORDON . Witter husband of Elisabeth Curren ; father of Eliza bpt. 9 Aug 1854 at Ballygalget Catholic Churchand more
2, Peter McGRATTAN bapt 19 nov 1828 at Ballygalget Catholic Church of Witter & Ballyphilip [ could peter be the son of hugh McGrattan] m Ann Gordon; father of
children . peter was a labourer so possibly moving around, he also put his mark so spelling might not be well recorded ]
2.1. Maryanne McGrattan b. 1858
2.2. Hugh McGrattan b. 6 Oct 1861
2.3. Elizabeth McGrattan bpt. 19 Aug 1862 at Ballygalget Catholic Church
2.4. Hugh McGrattan b. 6 Jan 1866 reg Downpatrick from familysearch.org also
https://civilrecords.irishgenealogy.ie2.5. Isabella McGrattan b. 19 Jan 1868 [may have m hugh Quinn 10 july 1906 reg Downpatrick irishgenealogy.ie]
2.6. Cecilia McGrattan b. 23 Feb 1871 (regd. Portaferry)
Catherine bpt. 13 Dec 1830 & Ann bpt. 10 Jul 1831 at Ballygalget Catholic Church
Ballygalget Ballyphilip or Witter 21: 62/54 a townland 4km NE of Portaferry; 289 acres; click here to see its location on a townland map; etcetc from Ros Davies
1823-1837 Tithes Applotment Books names listed by parish by Irish Genealogy Hub
McGrattan, John-Townland: Ballygraffin Year: 1834-Ballyhalbert-Down
McGrattan, Mary-Townland: Ballygraffin Year: 1834-Ballyhalbert-Down
McGrattan, Widow Townland: Ballygraffin Year: 1834-Ballyhalbert-Down
McGrattan, Wm.-Townland: Ballyhay Year: 1834-Donaghadee-Down
McGrattan, Wm.-Townland: Ballyhay Year: 1834-Donaghadee-Down
McGratten, Townland: Innishargie Year: 1834-Inishargy-Down
McGrattan, Edward-Townland: Bahernamaghery Year: 1833-Killinchy-Down
McGrattan, Widow Townland: Bahernamaghery Year: 1833-Killinchy-Down
the tithes were not well covered in the area most wanted
then Griffiths Valuation see from
https://www.failteromhat.com/griffiths.phpMc Grattan Mary Ardkeen Ardkeen Down
Mc Grattan Cecilia Ballygelagh Ardkeen Down
Mc Grattan Edward, Jr. Ballygelagh Ardkeen Down
Mc Grattan Edward, Sr. Ballygelagh Ardkeen Down
Mc Grattan Henry Ballygelagh Ardkeen Down
Mc Grattan James Ballygelagh Ardkeen Down
Mc Grattan Peter Ballygelagh Ardkeen Down
Mc Grattan William Ballygelagh Ardkeen Down
Mc Grattan Bernard Ballycraffan Ballyhalbert alias St. Andrew Down
Mc Grattan Daniel Ballycraffan Ballyhalbert alias St. Andrew Down
Mc Grattan Margaret Ballycraffan Ballyhalbert alias St. Andrew Down
Mc Grattan Anne Jane Ballymarter Ballyphilip Down
Mc Grattan Edward Broom Quarter Castleboy Down
Mc Grattan Daniel Cloghy Castleboy Down
Mc Grattan Hugh Loughdoo Castleboy Down
Mc Grattan Elizabeth Kircubbin Inishargy Down
Mc Grattan David Ann Street,Newtownards Newtownards Down
Mc Grattan Hugh Thomas Street,Newtownards Newtownards Down
for more information see
http://www.askaboutireland.ie/griffith-valuation/ I stop there to have your thoughts