The language in this game is atrocious, and not from it being badly translated, which is commonly in picking the wrong word because they sound similar (accept and except, or advice/advise for example). The issue(s) here is it's not incorrectly spelled words, or common mistakes, but the wrong words being selected in the first place, for example:
After Billy started fucking the Aunt's mouth (the very last scene in the game), she was simultaneously moaning exasperatedly and swirling her tongue with enthusiasm.
Exasperate, verb, generally meaning to irritate or provoke to a high degree; annoy extremely. So as written, she was either irritated or annoyed, while also enthusiastically using her tongue. Those two feelings/emotions are not usually paired up, unless the subject is actually being coerced/raped against her will... in this case she was willing, eager and wanted Billy's cock down her throat. Correct verbs to modify HOW the Aunt was moaning would include excitedly or eagerly, or by changing the sentence entirely, perhaps "hungrily accepted her Nephew fucking her mouth as she swirled her tongue with enthusiasm."
I'll give this about a 5/10; art assets aren't bad. Although as others have observed if the older sister is 18+, then the step-mother looks way too young, as does the Aunt although in the Aunt's case she could simply be the younger sister of the step-mother.
A possible solution is turn the step-mother into a full on Trophy wife (explaining why she's so young, and attractive), the Aunt is a younger sister, and the daughter(s) become adopted to explain away the ages being so close.
