Yes, many times, but not for titillation. I do it to teach the woman that her body is no longer her own. It belongs to me and I can do anything I want with it. I have a whole process I follow.
First, I call my girlfriend and let her know I’m coming over for sex. No mention is made of the other guy. I arrive with a friend. Ideally, it should be someone she does not know or knows only in passing. Rather than my fiend starting, I have sex with my girlfriend while he watches. Then he can have sex with her while I watch. We repeat this until we’re both sated. Afterwards I’ll give my girlfriend a nice reward, such as a dinner in a romantic restaurant, a gift, or even a weekend at a bed and breakfast (just the two of us).
To be effective this should be done after you have established a strong relationship with you woman, but before things have become routine. You’ll find that afterwards she is agreeable to anything you want, group sex, threesomes with other girls, etc.