I have had this idea stuck in my head for quite some time now and I would love to throw it out there incase someone is as fucked up as me and likes it lol. For this plot I am thinking about playing the adult younger brother and you play the older brother while we share the girlfriend role ( I would prefer it to be shared as it is much more fun that way but it’s that’s not your cup of tea we can definitely work something out). So we live in the city and live a comfortable life, you came from a small town in the countryside where your family still lives and managed to create a better life for yourself. You found a girl and settled down with her and after a few years when the relationship got stale you decided to have an open relationship with her. Pretty open minded for someone who lived on a ranch most of his life…. 

You get a call from your mother telling you that they are sending your brother out to the city for the summer to spend time with you and expire the city as he deserves it for working with his dad on the ranch all year. It’s is definitely a big adjustment for him and a culture shock to say the least when he gets to the city. He stays with you and your girlfriend at your apartment. While you’re at work most of the day, they grow close forming a bond. Her bold out going personality clashes well with his kinda shy more respectful tone. She also likes to tease and flirt with him a lot as it is always funny the way he gets all flustered and red. She finds it adorable…

Sometimes flirting with him infront of you causing you to think….. what would my brother look like fucking my girl… the idea is insanely taboo to you but at the same time turns you on so much. You start by easing him into it. One on one talks like what type of girl your like, what’s your body count, what type of porn you like. Then progress to more intimate stuff like jerking off to nudes of your girl or videos of her with other guys eventually leading to letting him fuck her. Later on even doing a threesome. Nothing brings brothers together like sharing a woman…. 

[F4M] We decided that the open relationship rule applies to your brother too…(detailed plot below)