Hello Meg
I have only had time for a quick look through the database as I am looking after my grandson who is ill at the moment so giving him all my attention. It would appear we have gone down the same path with reference to John Mortimer. I have his details on the 1901 census at 7 Bristol Terrace, Brithdir plus his wife Annie, 2 sons and 5 daughters. I also have him on the 1891, 1881 and 1861 but not on the 1871.
With regards to the name Gerrish; William Gerrish born about 1886 in St Thomas, Swansea came to Brithdir in about 1908/9 and took up residence in 1 New Bristol Terrace, with wife Edith Victoria who presented him with a son named William John born shortly after their arrival. Sometime later a Frank Gerrish born about 1893 in Treherbert, Glamorgan was a boarder in the household. There is no indication on the census form that William and Frank were related. However I note on FreeBMD the only two Gerrish marriages registered in Merthyr Tydfil district was:- Marriages Dec 1907 William GERRISH & Edith Victoria M TROTT and Marriages Dec 1911 Frank Gerrish & Eva M Trott. I assume you will already have these details but somewhere in the back of my mind I know I have come across the name Gerrish other than the census returns. I have two scrap books full of 50 years worth of newspaper articles on Brithdir and Brithdir people and I will look through these shortly, if I come across any refence to the name will post a scanned image on to you. I have not made the connection between the names Mortimer and Gerrish so if you can give me any details I will look further.
Regards for now, Roy