Ask the seniority of the Republic of China ...

If it's a servant, you can refer to the following:

The master's first wife is called madam, the second wife is called second aunt, and the third wife is called third aunt. The first wife of a gentleman is called a young woman, the second wife is called a mistress, and the third wife is called a mistress. The son of a gentleman is called a young gentleman; The first wife of the third young master is called Xiao San, the second wife is called Xiao San, and the third wife is called Xiao San.