Twincest 

When someone is sexually intimate, or develops an incestuous relationship, with his or her own twin.

1. "The McPoyles from 'It's Always Sunny in Philadelphia' are definitely guilty of twincest."

2. Person A: "Dude, did you see those two guys going at it? They looked exactly alike!"
Person B: "Yeah, man, didn't you know? They're in a twincestuous relationship."

Twincest by NecroManzie September 28, 2009

twincest 

When twins are in lust/love with eachother.

twincest by Anonymous September 14, 2003

Twincest 

When Twins are in love with one another and/ or like to perform sexuall activities together.

Benji and Joel are in alot of Twincest fics.

Twincest by Rhiannon December 8, 2003

TWINCEST 

Twincest
Gives new meaning to fo fuck yourself.

TWINCEST example: Hikaru Hitachiin and Kaoru Hitachiin
(if you dont know who they are, LOOK THEM UP)

TWINCEST by ASIAN >.< Wu-Dawgg May 7, 2010

Twincest 

Incest between any set of multiple birth siblings. Twincest can occur between twins, triplets, octuplets, etc. Twincest may also occur across gender lines (sisters, brothers, or both). Twincest can be any level of sexual intimacy.

The Visconti triplets practice twincest in homosexual pornography.

Twincest by T-Winner July 10, 2009

Twincest 

the hottest damn thing ever!

In The anime/manga series Ouran High School Host Club the Hitachiin twins(Kaoru and Hikaru) were called out on there twincest by Kirimi Nekozawa.

Twincest by sourxneonxgummixworms June 14, 2009

twincest 

A whole new way of 'go fuck yourself'.

When I saw those twins, all I thought of was twincest.

twincest by HarunaXV October 12, 2010