>be 12
    >sister is 7
    >rides in my lap on trip to Great Lakes
    >bumpy windy road
    >immediately get boner
    >so embarrassed I want to jump out of the car
    >hope to god she doesn’t feel it or know what it is
    >bump bump bump
    >she’s in summer clothes
    >cum in my pants
    >dick just pulsing while she sits there
    >completely fucking frozen
    >not even pleasurable because my heart rate is like 1000 bpm out of fear
    >she doesn’t even react or notice
    >feel like I was spared by god
    >fast forward 5 years
    >we are doing a trip to the Great Lakes again
    >memory of jizzing under sisters ass floods in
    >oh shit that was kinda hot
    >say sister should ride on my lap for old time sake
    >mom thinks it’s a cute idea
    >sister says hard no
    >why not
    >because
    >press her jokingly but she doesn’t answer, just says no I want my own seat
    >probably a good idea anyway
    >but why was she so against it
    >want her to sit in my lap not even for perverted reasons but now just out of brotherly spite
    >pack the car with lots of extra shit
    >only 3 seats open
    >looks like you’re gonna have to sit on my lap anyways
    >sister doesn’t say anything
    >start to get nervous
    >boner at this age would really fuck me up if she blurted it out to our parents
    >think about this with a half chub for minutes
    >okay maybe this is a bad idea
    >sister comes out with her bags “okay let’s go”
    >doesn’t look at me or parents
    >she’s wearing a sundress
    >holy fuck this is so bad
>”you know I can probably make space in this seat”
>dad says too late
>mom says it’s fine it’ll be so cute
>sister doesn’t say anything
>she climbs into my lap
>okay let’s go
>just my sister sitting on my lap
>no big deal
>sun dress under her so no bare panties on me
>mom “aww look at you guys”
>why are you so heavy sisteranon
>”I’m not”
>”this is really uncomfortable”
>”yup” she seems mad at me
>crisis averted
>guess I’m just not a horny 12 yo anymore
>but then
>we had yet to reach the bumpy windy road
>completely forgot that’s where it started last time
>sister starts vibrating and bouncing on top of me
>she’s a lot heavier so it’s less comfy, still no boner
>say “ow” every time there’s a big bounce
>sister just says “stop”
>she really is annoyed with me
>then she sighs
>she moves up on my legs leans forward and wraps her arms around our moms seat in front with her head resting against it
>”mommy anons being annoying”
>”anon what are you doing”
>wtf no I’m not
>mom asks if she want to sit on her lap
>sister just gunts, then after a few minutes moves her butt back onto my lap while still leaning forward against moms chair
>now her ass is gently resting on my dick instead of her full weight
>the second there was a slight bump I got a full erection
>dick shot up so fast I barely had time to react but catch it with a movement back so she’s back on my upper thighs
>actually scared for my life
>feel like I’m 12 again frozen in fear except this time it’s not about embarrassment, instead my entire relationship with my family is on the line
>sister comes off moms seat and sits back against me
>heart stops
>time stops
>I’m sitting as far back into the chair as I can, straight posture to keep boner away from her
>her ass literally sits right on the hard straight up tip of my dick
>I know she feels it and my life is over
>wearing jeans so if I don’t say anything maybe she’ll think it’s the zipper
>bump
>OW
>almost snaps my dick
>push her off me and adjust quickly
>”what?”
>”my belt was pinching me”
>hard on is now resting in left waist crease
>sister sits back
>feel like it’s kind of noticeable but pretty sure I’m in the clear
>dick just barely out of danger zone against her upper butt/lower back
>just enjoy a comfy hard on for a few bumpy minutes
>she moves back
>her bony ass literally crushes my dick
>makes me gasp
>no way she doesn’t feel my boner
>try to divert with an OW and
>”mom tell sisteranon she’s way too heavy and has to sit up”
>sister says oh my god like she’s almost disgusted
>mom tells us to shut up cause we are almost there
>she sits back with full force
>push sister and whisper “you’re hurting me”
>she reacts with another butt jab and I feel like I might cum
>don’t know if she knows what she’s doing
>”mom”
>”fiiiiine” my sister sits off me
>”mom thanks her for being easy”
>I’m just trying to keep up with my heartrate
>sister falls back so her back is to my chest with a loud sigh
>pulls her butt up to my waist
>full stroke of my dick
>start cumming
>very hard pulsing
>The second she feels it she goes “oh my gawd” and jumps back to hugging moms chair and sitting on my leg
>the unorthodox stimulation made me only cum a few ropes but it was enough to soak me
>can’t think, just breathing 
>sister doesn’t say anything
>don’t know what the fuck I should do or say
>pants now wet if she sits back
>mom tells us we are coming up on the hotel
>sister says she thinks I enjoyed the trip
>”did you anon” says mom
>”no”
>sister laughs
>is this really happening
>start to think how the fuck am I going to get out of the car
>we get there
>say I wanna change into my bathing suit in the car so I can go straight to the pool
>sister protests to mom “that’s so weird... do it in the bathroom” etc etc
>mom agrees
>we pull in
>sister aggressively puts her mouth to my ear and says “pervert” like she was stabbing me with the word as she jumps out of the car