Hello Gower

Which Gelli Gynar Farm do you mean? What information do you have about the Jones family? Do you need census info, BMD, etc?
At Gelli Gynar Isaf I found Henry Jones, farmer of 70 acres employing 2 labourers in 1881, with daughters Mar and Hannah, son Henry, and baby Granddaughter Hannah.
RG11 Piece 5430 Folio 64 Page 6
He was still there in 1891. John Jones was at Gelli gynar Uchaf, farm of 75 acres.
If you could be more specific, it will help avoid wasted effort.

Kind Regards
Morgan