Mair Saunders Jones, the daughter of Saunders Lewis, one of the founders of Plaid Cymru, has died.
A public service will be held on Monday at St Joseph's Catholic Church in Penarth, Vale of Glamorgan.
Mrs Saunders Jones was one of the editors of Saunders Lewis: Letters to Margaret Gilcriest, which detailed correspondence between her parents.
She was the mother of Marged Elen, Siwan and Dyfrig, and a grandmother to five.
Mrs Saunders Jones was born in 1926, the year after her father helped to found Plaid Cymru.
She died in Llandysul, Carmarthenshire.
Her death notice in the Western Mail described her as a "nationalist and lover of Chateauneuf du Pape".
It asked for any donations to be sent to Cymdeithas yr Iaith Gymraeg, the Welsh Language Society.
Her father was a writer and politician, and a BBC radio lecture he gave in 1962, Tynged Yr Iaith (The Fate of the Language), helped to lead to the foundation of Cymdeithas.
Mr Lewis lived in Penarth and died in 1985 at the age of 91.