William Dillwyn was descended from his grandfather, also William Dillwyn who emigrated in 1699 from the
Breconshire to settle in the
Welsh tract of
Pennsylvania. William married Sarah Logan Smith on 19 May 1768, in
Burlington County, New Jersey. Together they had a daughter Susanna, born in New Jersey, on 31 March 1769. She married Samuel Emlen on April 16, 1795. William remarried on 27 November 1777, to Sarah Weston in
Tottenham, then in
Middlesex. Their children were: •
Lewis Weston Dillwyn (1778–1855) • John Crook Dillwyn (1780–1781) • Judith Nickolls (Dillwyn) Bevan (1781–1868) • Ann Dillwyn (1783), married
Richard Dykes Alexander of
Ipswich • Lydia (Dillwyn) Sims (1785–1830) married John Sims –
William Dillwyn Sims was their son. • George Dillwyn • Sarah Musgrave Dillwyn (1790) • Gulielma Dillwyn (1792) Through his son
Lewis Weston Dillwyn and his wife, Mary Adams of Penllergaer, Llangyfelach, he was the grandfather of noted photographer
John Dillwyn Llewelyn (1810–1882), MP for Swansea
Lewis Llewelyn Dillwyn (1814-1892) and pioneering female photographer
Mary Dillwyn (1816-1906). His great granddaughter by his grandson John was the Welsh astronomer and pioneer in scientific photography
Thereza Dillwyn Llewelyn, and his great granddaughters by his grandson Lewis were the novelist and industrialist
Amy Dillwyn and lepidopterist
Mary De la Beche Nicholl. == Commemoration ==