Brandir's dates come from an otherwise unpublished genealogical chart in volume XI of The History of Middle-earth. This leaves their canonicity open to question, but note that Brandir's year of death, I 499, corresponds with the date of the slaying of Glaurung established in other sources, making it very likely to be correct.

Brandir's mother Beldis isn't named in any canonical work, but she is referred to in volume XI of The History of Middle-earth. Her line of descent was significant, because her own elder brother was also known as Brandir. It seems therefore that the later Brandir gained his name from his uncle.