To see a mirror in your dream symbolizes a loved one or good friend. Dreaming about a mirror is also symbolic of the truth.
To see your husband in your dream signifies the waking relationship with your husband and the subconscious feelings you have towards him. The dream may be trying to focus on hidden elements that you are not addressing in your waking life.
To see your mother-in-law in your dream implies that there is some unresolved issue or inner turmoil that you need to work through. Your waking relationship with your mother-in-law will prevail in this interpretation.
To see others having sex in your dream refers to your own desires of being more adventurous in your own sex life.
To see your parents having sex in your dream indicate that you are seeing similar aspects between their relationship and your current relationship.
Maybe you’re seeing elements of his mother in him, possibly negative ones that you want to address?