descendancy
Noun
Meaning
(uncountable) The quality or condition of being a descendant.
(countable) Descendants considered collectively.
(uncountable) The opposite of ascendancy; the condition of being in the process of losing power or control.
Source: en.wiktionary.orgAntonyms
Examples
Note that descendancy of the Julii Caesares before the generation of Julius Caesar's grandfather is in part conjectural, but as presented by scholars.
The claims might have been made to ensure a descendancy of nobility, considering only a high placed family can be made such a position. citation Kings of the Akkad Dynasty.