(covers information from several alternate timelines)
Soh-chIm was a Klingon word which had no direct translation, but was most closely approximated by "stepsister/brother" and similar to the Human concept of a "godparent." A Klingon parent bestowed this title upon a respected adult friend. If accepted, the Soh-chIm would be responsible for their child's future well-being in the event that the parent(s) could no longer do so, typically when the child's parent(s) went into battle and the odds were against returning. This agreement was legally binding and was well-recognized in Klingon law. The Soh-chIm was usually someone who was a close family friend and already familiar with the child in question.