Corporal Kosti was an ImpSec gate guard who was given the job of watching over Vorkosigan House after Aral and Cordelia Vorkosigan left to live on Sergyar. It was a quiet job even after Miles Vorkosigan returned from his last galactic mission.
To while away the time, he made a pet of a feral cat that ran afoul of the tangle-field trap protecting the house; he named her Zap and she and her kittens eventually became members of the Vorkosigan household. He also got Ma Kosti-boxed-lunches brought to his guard-post by his brother until Simon Illyan moved in and more guards were brought in to improve the security of the building.