Philip III was a member of the Bolanden [de]-Falkenstein family, which were originally based at Falkenstein Castle [de], in Donnersbergkreis in the Palatinate and had held part of the Münzenberg Inheritance in Wetterau since 1255.
Philip had a large water castle built at Lich, in order to protect the spot where the Lange Hessen [de] road crossed the Wetter river.
In 1313, Emperor Henry VII promoted Königstein im Taunus to town rank as well, which had formerly belonged to the Nürings [de] and had been part of the Falkensteins' domains since 1255.
A long-running conflict with Ulrich I of Hanau over the Münzenburg Inheritance and especially the Jewish tax of Assenheim [de] and Münzenberg was brought to an end in 1304 with an arbitration in Philip's favour.
They had the following children: He married, secondly, in 1303, Luckard(e) of Isenburg (died 11 October 1309), an illegitimate daughter of Ludwig I of Isenburg von Cleeburg, Burggrave of Gelnhausen, with whom he had the following children: He married thirdly, on 11 October 1309, Mechtild of Hesse (1267 – after 1332), widow of Gottfried VI [de] of Ziegenhain [de], daughter of Landgrave Henry I of Hesse and Adelheid of Brunswick, who was a descendant of Saint Elizabeth of Thuringia.