Threesomes and moresomes aren't everybody's cup of tea, plus unless you have total faith in your partner and vice versa, such shenanigans are probably best avoided as they have been known to seriously undermine relationships. In my experience, our relationship which was strong already was made all the stronger through exploring such things.
At the age of five, Skagra decided emphatically that God did not exist. This revelation tends to make most people in the universe who have it react in one of two ways - with relief or with despair. Only Skagra responded to it by thinking, 'Wait a second. That means there's a situation vacant.'