A more thorough explanation:

PRONEPOS

Pronepos is a Latin term used in Roman and civil law to refer to a great-grandson.

Plural form: pronepotes.

• My father's father's father is my pronepos.
• According to the will, the estate will be divided equally among the testator's children, grandchildren, and pronepotes.

The examples illustrate that pronepos refers to a person's great-grandson. In the first example, the speaker identifies their father's father's father as their pronepos. In the second example, the term is used in a legal context to specify that the estate will be distributed among the testator's children, grandchildren, and great-grandchildren.