Little Brother is a phrase that is commonly used to refer to a younger male sibling. However, there are several synonyms that can be used to describe the same relationship. Younger brother, baby brother, kid brother, junior brother, and little bro are some of the popular alternatives to the phrase little brother. These synonyms can be used interchangeably, depending on the context and the relationship between the siblings. Each synonym carries a unique connotation, with some emphasizing age difference, while others highlighting affection or familiarity. Ultimately, the choice of synonym depends on the speaker's preference, tone, and the level of intimacy between the brothers.