We call Mom in

"Mom! We need your help!" Mom comes into the dining room. "What are you two doing? OMG! Your doing anal! No no no! Her ass hole is way to small for that." She walks over and feels around her anus. "Well let me go get some lube"

She walks off into her room and brings back a small container. "You see this is lube. You are supposed to use this for anal. Now let me try to get it out." She runs it around sisters cute little butt. "Okay pull." I start to pull. Sis begins to cry. "This hurts so bad. I'm never doing this again." After a few seconds boom! We're free! Mom goes back to her room and sis waddles away. "I'm not gonna be able to sit for a week!"

Days later sis ask me to take her to the store.