Its diagram is as follows:
6 × 3 = 18
Mother: 1 → 3 shares
Grandfather: 1 → 5 shares
Brothers: 3 → 10 shares (5 each)

Fifth case: the grandfather’s muqāsama (proportional division) equals a fixed one-sixth of the estate, and both are more advantageous for him than taking one-third of the residue. An illustration is a husband, a paternal grandmother, a grandfather, and one brother, a configuration in which the prescribed shares consume two-thirds of the estate and the number of brothers equals the grandfather.

Why muqāsama and the sixth coincide is this: once the husband’s half and the grandmother’s sixth are deducted, two parts remain for the grandfather and the brother. The grandfather therefore receives one part—whether by muqāsama or because it represents the sixth—and the brother takes the other part.

Its diagram is:
Base 6
Husband: 3 shares
Grandmother: 1 share
Grandfather: 1 share
Brother: 1 share