Complex sentence: In 1617 he inherited the estates of his aunt, Barbara of Ursel, last heir of Lacelot II of Ursel, on the condition that he and his heirs in perpetuity change their name and coat of arms to d' Ursel.
Split into simpler sentences: In 1617 he inherited the estates of his aunt, Barbara of Ursel, last heir of Lacelot II of Ursel. She asked the condition that he and his heirs change their name and coat of arms should be changed in perpetuity to d' Ursel.