Irma Crabbe was the wife of Pollux Black and mother to his three children:
- Walburga Irma Black (1929-1985), who married second cousin Orion and had two sons.
- Alphard Pollux Black (1930-1977)
- Cygnus Black III (1931-1992) who married Druella Rosier and had three daughters.
As she was younger then Pollux and attended Hogwarts with him, she was born no later then 1918, but it's most likely they were in the same year because they married after Hogwarts and had to be of age by then. She gave birth to Walburga quickly after Hogwarts.