Charles Thornely, coastal marine painter, often misleadingly called William or William Charles, was son of John Daniel Thornely (c.1788–1848), a wealthy Liverpool merchant trading to the USA, and his wife Ann, née Lomax, (m.1815, Liverpool), who had 13 children. John’s elder brother and business partner was Thomas Thornely (1782–1862), Liberal MP for Wolverhampton and at the time of the latter’s death Charles and six of his brothers were his surviving nephews through John.

The birth entries of Charles’s elder ten siblings up to 1829 appear in Liverpool non-conformist records but there seem to be none for the three youngest children, including Charles and his twin Edward (both apparently born in late 1832 or early 1833). While the baptismal record is missing, why Charles is often called ‘William’ is uncertain, since this does not appear in other formal records, unless by later confusion with William Anslow Thornbery, who seems also to have used the name Thornley (but in that variant spelling). His mother died in April 1836, when he was three, and their father only re-married six years later.