Theodicius dux…restituit…et…Hildeprandus dux noster fecit. No reason for Hildebrand to fulfill Theodic's will, if he wasn't his son, Hildebrand fled to Rome when Charles I King of the Franks invaded Italy in 773, returned following year and was appointed Duke of Spoleto. He was after his death succeeded by the Frank Winichis as dux of Spolet, meaning, another person from another family and not related to the previous dukes.
THEODICIUS (-before 9 Jun 776). "Carolus…rex Francorum et Langobardorum" confirmed the properties of Farfa monastery by charter dated 9 Jun 776, including property which "Theodicius dux…restituit…et…Hildeprandus dux noster fecit"[881]. The Chronicon Farfense records that "Theodicius…dux" donated "casalem Paternionem qui pertinet ad curtem Germanicianam" to Farfa[882].
https://fmg.ac/Projects/MedLands/CENTRAL%20ITALY.htm#_Toc246900380
Early abbacy (770–72)
During his tenure Farfa secured thirty donations, more than three-quarters of which were gifts outright. He also received from private citizens one confirmatio (confirmation of a prior acquisition) and one promissio (promise of a future donation in land), and increased
Farfa's lands by purchasing private property on one occasion and exchanging it on four others to rationalise the abbey's holdings.[3] In 772 Desiderius, who had up to that point been acting as Duke of Spoleto, bestowed that office on >Theodicius, who proceeded to make a grant to Farfa<.
Farfa and the fall of the Lombard kingdom (773–74) Probatus may also have been the beneficiary of a famine that struck Italy in 774–75,[5] and caused an increase in the charitable donations.
Likewise the threat of war may have influenced Duke Hildeprand of Spoleto to procure divine favour or vouchsafe his land to God by donating it to the abbey.
The charters of three grants the duke made to Farfa credit the monks with suggesting them, a sign of Probatus' gift for diplomacy.
https://en.wikipedia.org/wiki/Probatus#Early_abbacy_(770%E2%80%9372)