Things are heating up at the summer barbeque where you're introducing your new girlfriend Marie to the family for the first time. Unfortunately, she's also caught the attention of your dyke of a big sister Kristen, who's been being awfully flirtatious with her. However, it isn't until a trip upstairs to turn on the AC leads to a big shock waiting for you in your own bedroom! So now it's up to you. Is it time to finally teach your sister a lesson with the power of cock, or is it time for Marie to experience her first threesome? Or maybe you just want to experience some good old fashioned NTR and sit back while your Big Sister shows you how to really pleasure a woman. After all, she knows best!
The prompt is kind of long, so it might be easier to cut it into a few pieces and paste it accordingly, ignoring any input the AI gives you until the full thing's in there.
Also, when I wrote this, I imagined the big sister looking like Kristen Stewart, when she was in peak dyke mode, with some added tattoos because tattooed lesbians are hot. Feel free to change up the look of your big sis however you want.