We have Hermann von Württemberg (Württemberg-48) as father of Ulrich I mit dem Daumen von Württemberg. This appears to be based on Hansmartin Decker-Hauff whose theory is widely not accepted as insufficiently sourced. Many historians follow Paul Friedrich Stälin who holds Ludwig III as the likely father. Hermann should be disconnected as father and either Ludwig III attached as uncertain or the parents should be left unknown.
Edit: corrected typo.