Dev, don't be too upset, but some people are asking the right questions. She (no matter if she's Aunt or Mom's friend or whoever she is) is on the cover of your game, which means she's clearly not some kind of side story character. That's why questions arise about family members, and as I understand from your answer, they won't be involved in sharing/swinging scenes.
But to clarify, will sharing/swinging be the main part of the game or will it be isolated scenes (as I understand all this will be unavoidable, judging by the MMF scene)?