They interpret kinship on a different level. Amethyst has called the Crystal Gems her family due to shared experiences, as well as the other Earth Amethysts who she shared immediate kinship and loyalty with because they all came from the same place with the same pre-programmed knowledge.
Human varieties of kinship seem to amuse them. For example perma-Fusions are clearly romantic, but as non-reproductive drones they didn’t have an explanation for it other than just considering themselves part of a whole until borrowing the concepts and traditions of romance from humans.
White Diamond is the first of her race as far as we know, and as far as we know there are no Gems older than the four Diamonds who she created, making her likely the mother of all Gems. Sugar outright said her role towards the Diamonds is motherly, but no Gem seems to acknowledge their creator at all and instead regards their planet and Kindergarten as their instinctive family first and whatever Diamond they belong to as their matriarch second with lesser subservience to the other three Diamonds. White Diamond is motherly, but not seen as a mother. Aside from Crystal Gems and the Diamonds, mentoring in general doesn’t seem to be a thing.
So basically they only have two types of relationships, three for Off-colors, until they spend time with humans and give labels and categories to their connections.