Who Wears A Tux

My husband- to- be`s parents are divorced. His Dad is coming to the wedding. They are pretty close. It is a large wedding with all the hoopla. His dad is remarried. His mom, who we are really close too, has been with a man that we really like and she has been with him for a long time. How should he be included and should both of them (his Dad and his moms boyfriend) wear a tux?