There's not enough information to say exactly who the little brother is. He could be an ordinary boy in a family who is the youngest among his siblings.
There are different Christmas stories. For example, in the story of the Nativity, Jesus is often the central figure, and if we consider Joseph as a 'big brother' figure in a sense (as Mary's husband), then Jesus could be seen as a 'little brother' in the context of God's plan for humanity. He is the one who brings the message of hope and salvation, which is central to the Christmas story.
The little brother is Randy. He has his own quirks, like his strange eating habits. For example, he doesn't like to eat like a normal person and has some really funny moments when it comes to food during the Christmas time in the story.
Well, if we think about some modern Christmas stories or movies, there might be a little brother character who is part of a family's Christmas adventure. He could be the one who discovers the magic of Christmas in a new way, like finding a hidden present that leads to a whole new understanding of the holiday spirit for the family.
In 'A Christmas Story', the little brother is Randy. He is a memorable character in the story, often getting into various situations with his older brother.
The little brother often plays a crucial part. He can be the character that needs protection or guidance. For example, in some stories, he might get lost on Christmas Eve while looking for the perfect Christmas tree. His misadventure then leads to a series of events where the family comes together to find him and in the process, they rediscover the true meaning of Christmas which is about love and family.