Only fucking scenes can't make an incest story specially mom son incest story extremely hot and erotic. The elements that make it extremely hot and erotic are good plots, excellent themes, suitable characters setting ,related situation narrations, making different situations and the most important elements are erotic, exciting and double meaning naughty conversations among the characters. You are really doing very well in this field. And I heartily request you to apply more such kinds of elements in this great story. Hats off to you my dear writer.