The Londonderry Sentinel of 26 February 1925 carried a death notice for William Anderson of 34 Lower Bennett Street who died on 24 February, saying that his remains were to be interred in Moneyreagh Burying Ground.
I can see a marriage on 27 June 1928 for William and Catherine's son William to a Mary Patterson, it was in the Registrar's Office in Derry, William was described as a bachelor, a factory worker living at 34 Lower Bennett Street, the son of William Anderson a shirt maker, spinster Mary's address was Ardmore, her father given as John Patterson a bleacher, the witnesses were James Anderson and Ella Robinson.
Also a possible marriage for William and Catherine's daughter Isabella Anderson at Ebrington Presbyterian Church on 8 August 1922, the groom was John McLaughlin of Derry, a bachelor and a 'Special' by occupation (police), his father's details were not provided, the bride was Isabella Anderson of Bennett Street, spinster, the daughter of William Anderson, his occupation given as 'shipyard', the witneses were Joseph A. W. Reaney and Margaret McLaughlin.
Also a possible marriage for William and Catherine's daughter Jane Anderson to a James Lee at the same church the previous year:
https://civilrecords.irishgenealogy.ie/churchrecords/images/marriage_returns/marriages_1921/09233/5341233.pdf