Cousins and nephews of the title holder can’t be heirs apparent

The heir apparent is the person who

• is first in the order of succession, and
• cannot be displaced from inheriting when someone else is born.

A cousin or a nephew would normally be an heir presumptive, which is a person who is currently first in the order of succession, but who can be displaced if the current titleholder has a son (or, rarely, depending on the inheritance conditions of the title, a daughter). It doesn’t matter if the title holder is old, celibate, unmarried, or even medically impotent. As long as he lives, the rules presume he can father a child of his own.

Only heirs apparent get to use one of the title-holder’s lesser titles. The title holder doesn’t get to decide who gets the title. The order of succession is set up in the papers that established the title. Usually, heirs male of the body, which means the first-born son in a direct line.

The title-holder can’t give away lands that are entailed to the title, either. An entail leaves the lands to a future title holder, with the current title holder having right of possession. You cannot give away or sell what you don’t own.