Ur sister mister is the next level of ur granny tranny. It is stronger than ur mom gay, ur dad lesbian and ur granny tranny combined. Nobody who ever heard this sentence is alive.
John: Hey Jeff ur mom gay Jeff: No u
John: Ur dad lesbian
Jeff: Ur granny tranny John: Ur sister mister
Jeff: *jeff and his whole family instantly die and go to the deepest layer of hell*
The worse possible insult above "ur mom gay" "ur dad lesbian" "ur granny a tranny" and "ur granpap a trap"
James: lol ur mom gay Holden: ur dad lesbian
James: ur granny a tranny Holden: ur granpap a trap
James: well ur sister a mister
Holden: *shrivels up and dies*