Now 17-year-old Kylie's sister Kim, 34, has defended her decision to have the temporary procedure.
Speaking to Access Hollywood at the launch of her new book Selfish, Kim said: "At 10 and 11 years old she'd say, 'Kimmy, how come my lips aren't as big as your buys'?"
Acknowledging Kylie's lips were an insecurity, Kim added: "If it's going to make her feel better then I'm all for it."
Kim also hit back at critics who have slammed Kylie for lying about having the procedure.
"She didn't lie, it took her a while to actually make that decision and once she decided to plump them, she was still over-lining, then sometimes it would look too big, then she figured out to stop over-lining.
"She plumped them and she was happy with it. People think, 'Oh my God she lied for so long – now she's finally come clean' but that's not the case, it took her a while to do it."
In a a teaser for an upcoming episode of Keeping Up With The Kardashians, Khloe, 30, can be seen urging Kylie to come clean about the fillers.