H.N. Beilby spent a whole winter gathering information about all the bitch strains and called them "families." He identified over sixty of them and gave them numbers as opposed to the males, who are identified with letters.

The "family" described by H.N. Beilby requires a bitch with offspring in at least three generations and a reasonable number of registered dogs to be reckoned as a "family strain." Beilby refers to the early days of specialised livestock breeding, and to the later "Bruce Low" system, when he writes about lines and families. In the early days it was considered adequate if the sire was of good enough quality and a good representative of the breed, and that a good sire on his own would correct the faults of the bitch.

The Bruce-Low system emphasised the importance of a good bitch strain in producing good offspring. In the 1940s, we know that everything about the families was all handwritten, and as far as we know, they were never published as a full collection. As we unfortunately do not have information about all the sixty or so identified bitch strains, we have not been able to research fully about what strains are still active.

Males are referred to as being from the "-line," and this is passed on along the sire strain (sire's sire's sire etc.) You can read more about the male "Lines" here.
Bitches are referred to as being from the "-family," and this is passed on along the "bitch strain" (dam's dam's dam etc.)
If the last male of a line dies without male offspring, the line ends, same for a dam's family. An offspring of said lines and family could then be from, for example, M(line) 22 (family). More information about the families will be published soon.

Below is a selection of bitches we have researched, along with the number of descendants continuing their family line. In the last column we have made a list of the bitches from their family which we assume is within an "active age of breeding" - in this case 8 years old.