Guillaume was the son of unknown parents. The date and place of his birth have not been found.
His wife was Maria Isabella Godofreda von Thurn und Taxis. They were married, but the date and place have not been found. They had no known children.
| Attribute | Date | Description | Details | Source | Multimedia | Notes |
|---|---|---|---|---|---|---|
| Nobility Title | comte de Lannoy | |||||
| Nobility Title | baron de Wignacourt |