Guillaume was the son of Alain I de Tinténiac but his mother is unknown. The date and place of his birth have not been found.
His wife was Eremburge. They were married, but the date and place have not been found. Their two known children were Olivier I (?-?) and Tiphaine (?-?).
| Attribute | Date | Description | Details | Source | Multimedia | Notes |
|---|---|---|---|---|---|---|
| Nobility Title | seigneur de Tinténiac |