Most often when you dream of making love with a familiar person it reflects your desire for a certain aspect of their personality traits that you lack, or feel insufficient in.
For example, I used to dream of having very intimate and intense sex with my university lecturer, yet in waking life, we had never related in any way.
She used to be very eloquent, bold, and smart. These were the traits I needed as I was finding it a challenge to make YouTube videos as I was not as eloquent as I desired.
However, if you have feelings for this person, then the dream is drawn from your fantasies about them. This happens a lot especially when you have a hard crush on your boss, colleagues, friends, coach, etc. Therefore, work on your mind and heart. 
Dreaming of having sex with a celebrity.
Dreaming of getting intimate with a celebrity reflects your obsession and desire toward that person.
You may be attracted to them due to a specific aspect of their personality that your spouse lacks.
Perhaps, the male celebrity is more handsome and masculine than your husband.
Or probably, the female celebrity is more fair and independent than your wife. Whatever attracts you to that celebrity may differ from person to person.
This has the effect of drawing your heart and affection away from your spouse. You become attached to fantasy, that’s why it manifests in your dreams.
This act is sinful, as you are lusting after a stranger. Be realistic and learn to be contented with what you have, because it’s the best.
What happens when you have sex in a dream?
Spiritual spouses, which are simply marine spirits cause stagnation in your life.
If you were to attend a job interview but end up dreaming of having sex, then you will be disqualified from the position you are applying for.
When you have sex in your dreams before exams, then you are doomed to fail.
