Being Mary Elizabeth (Lloyd) Griffiths was born about 1876 (using the age from the death registration), possibly your Griffith Griffiths was actually born before 1884 even tho he gave his age as 32 when married in 1916??
1881 Census -
name: Griffith R Griffiths age: 0 gender: Male birth year: 1881 birthplace: Wales relationship to head of household: Son marital condition: Single profession/occupation: address: Gilvach census place: Llanychaer, Pembrokeshire, Wales disability: record type: Household family history library film: 1342306 the national archives reference: RG11 piece/folio: 5424 / 66 page number: 7 HouseholdGenderAgeBirthplace headHugh GriffithsM42Wales wifeEliza GriffithsF38Wales daughterMary J GriffithsF6Wales sonWilliam R GriffithsM4Wales daughterMartha A GriffithsF3Wales daughterHannah L GriffithsF1Wales sonGriffith R GriffithsM0Wales boarderHugh W HughesM57Wales
Births June Quarter 1881 GRIFFITHSGriffith RichardHaverfordwestVolume 11aPage 978