Can you suggest some realistic scenarios, they can be quite challenging to write.
Well, first , as artists/creator/storywriter you should have some key points: in this case, i would start from how these two women looks - we all agree i guess that we are talking here about age approx. 38-45, so let's say sons are anywhere around "18" to 24 (quotes are for legal reasons ha ha... i mean clearly in fantasy we all know this or that "son" character could easily be 16, or something like that) . Now, family environment and whole situation could be various and different. From divorced, modern day single mother, to seemingly perfect, classic suburb family with nice home, pool, three cars and stuff. Also, again, mom could be also "perfect" wife, with maybe suddenly conflictual mother/son relationship, with son becoming increasingly nervous because either his friends are making too many remarks about how his mom looks, or it's himself who has to deal with new sensations about his moms body and all. It could be family that are going through heavy crisis (like many in real world) fights and bad atmosphere, it could be classic case of "oedipus complex" and so on... I personally would always create some kind of conflictual and tumultuous relationship between mom and son, with son's character becoming more and more manipulative, driven by his sexual instincts, and focused on how to fuck that hot mature woman that is his mother... So yeah, key points would be: moms looking and dressing as everyday women, that could easily be our neighbor, son just a high-school guy growing up and changing, becoming a man , with his manipulative, bastard side, constantly aroused by his mom's body, tits, ass, pussy... 2. point entire story should be based on him seducing and convincing mom to have sex, repeatedly... 3. Her having constant feeling of guilt, regret, trying to resist, but for many reasons, just being unable. Once sex starts, he turn out to be pretty hard-good-passionate at it, so she keep giving in. Then again, there could be literally hundreds possible plot variations: family sex therapy, influence of a friend (his or hers), going out together and becoming more friends than mom/son (i guess relatively frequen situation in modern western society, in every social class i guess...). Any type of individual morbidity (him being horny teenager is almost given/granted , but maybe even modern day 40 yrs old woman could easily find herself ready to be fucked by younger , big and hard cock...). To me, important thing is to avoid bullshit like "son's cock is hurting, mom is helping..." , "mom found son masturbating..." , any type of magical rings, books, beverages... Just think about what you could really read in news, or hear from a therapist, real life cases.