Indiana Family Law - Step-parent visitation?

What rights does a step-parent hold in regard to visitation with my son? I hold physical custody of my son. My ex works nights and refuses to allow me rights to visitation while he is at work. He's remarried so my son is in the care of the step-mother while he's at work who constantly verbally badger's my son, talks mean, and my son pretty much hates her. My ex believes she is the perfect step-mother on the contrary. I have filed a modification of parent visitation and have a pending hearing in May. My ex states that his wife (step-mother) is an extension of him and she has the right to vsitation instead of me during his scheduled visitation. Does anyone know the answer to this or have gone to court over this very same issue?