Marius Black

Marius Black was the third eldest child of Cygnus Black I and Violetta Bulstrode. Marius was disowned and removed from the Black family tree for being a Squib, as his family believed strongly in the importance of blood purity and disdained Squibs, who are generally treated as second-class citizens in the wizarding world.

His date of birth is unknown, but given when his siblings were born, Marius was likely born between 1915 and 1920.

Etymology
Marius is a Roman name derived from the Roman god of war, Mars. It was the name of several Roman generals, a philosopher, and an emperor. One of those Roman generals was renowned for his revolutionary military reforms and for being elected consul an unprecedented seven times. The name is also sometimes used as a masculine version of the name Maria, which is derived from the Hebrew name Miriam, the meaning of which is usually theorized to be "sea of bitterness". Marius is also the name of one of the main characters in Victor Hugo's ''Les Misérables.