List my sister's name and her husband or list my sister's name and my brother in law? How should I write this in program?

Please be more specific - isn't your sister's husband the same person as your brother-in-law? Perhaps you are asking how to list your sister's ex-husband?

If listing family members the form to use depends on how formal you want to be. For formal programs you might list a married couple as "Mr. and Mrs. John Q. Smith, parents of the bride." A less formal way would be: "John and Kate Smith, parents of the bride." If John and Kate are divorced you might list them on separate lines: "John Smith, father of the bride," and "Kate Smith, mother of the bride."

The wedding is for my niece. She wants to list all family members in wedding program. She has multiple aunts, sisters of her mother. She wanted to know when she listed sisters of the mother of the bride should she write, sister and husband or sister and brother in law.