The origin story of baby reindeer often starts with the mating season of adult reindeer. Female reindeer carry their calves for about seven and a half months. When the time comes, they give birth in areas that provide some shelter from the harsh elements. Baby reindeer are born with a natural instinct to follow their mothers. Their origin is deeply tied to the cycle of life in the Arctic regions, where they have to adapt quickly to the cold climate and find food among the lichens and grasses. Over time, they become an important part of the Arctic ecosystem and are also associated with the magic of Christmas in many cultures.
One key element is the environment. The Arctic climate is crucial as it's where they are born and grow. Another is the reindeer herd. The social structure of the herd provides protection and guidance for the baby reindeer. And of course, the role of the mother reindeer is very important in the origin story as she gives birth to and nurtures the baby reindeer.
If we consider a more general view, in some regions where reindeer are native, baby reindeer might be part of a herd managed by indigenous people. The cast (assuming you mean group) of baby reindeer would grow up learning from the older reindeer in the herd. They'd learn how to forage for lichens, which is a major part of their diet, and how to migrate to different areas depending on the season. Their real story could involve survival in harsh Arctic or sub - Arctic climates, dealing with snowstorms and limited food resources during the long winters.
I'm not entirely sure. It might be a real story if it's based on someone's actual encounter with a baby reindeer in the wild or on a reindeer farm. However, it could also be a fictional story made up for entertainment, like in children's books or movies where baby reindeer are often depicted in magical or anthropomorphic ways.