I was downstairs in the laundry room when my 13 year old daughter and her friend came home. They didn't think anyone was home, because they came downstairs into the basement living room, they sat down on the sofa and started to make out. I was down the hallway across the hallway, I could see into the living room threw the crack of the open laundry room door. I thought of making noise so they knew I was in the laundry room, but I didn't. I watched them kissing and feeling each other under there clothes. My daughter pulled her top off over her head, her girlfriend undid her bra and put her mouth around her small tits. To be honest my cock was rock hard and throbbing in my pants, I was very turned on seeing them having sex. My daughter's girlfriend was the same age as our daughter, but her tits were a lot bigger. They made out on the sofa eventually taking off there jeans and panties and eating each other out. I was masturbating while watching my daughter between her girlfriend's thighs with her ass in the air and her pussy lips in plain sight. My wife drove into the driveway and they quickly got dressed. I can't stop masturbating with that experience playing in my head, I get really excited remembering my young daughter naked and seeing her pussy, I get a erection from the thought of her having lesbian sex.