Wilhelm, who married Isabel Nel in the year 2000, already has published several genealogical publications, including his magnum opus that appeared in 2015: "Die Familiegeskiedenis van Corli en Anica Bernhardt" (The Family History of Corli and Anica Bernhardt). In it he explores the ancestry and history of his two daughters on both the paternal and maternal side (32 families in total), down to the respective patriarchs and mothers.
He is a strong supporter of a holistic approach to genealogy, and thus promotes pedigree research, as well as the broader concept of science-based family history writing. In 2020 he won the GSSA's award for best article in Familia, and in 2021 he was elected chairman of the GSSA's Northern Transvaal branch. When he is not engaged in genealogy, he spends his free time writing history, collecting books, restoring classic cars, riding motorcycles, travelling with his wife, snooping in antique shops and markets, and just hanging out in his garage to tinker with all sorts of things.