FireFly is not - while described as full service, it operates separately, and indeed was more LCC when running the 737s
MasWings is
Jetconnect (Qantas NZ base) and QantasLink are
JLs subs J-Air and JTA are afaik
BAs Comair is (albeit not IAG owned)
The LCCs Jetstar (QF), Jetstar Asia (QF), Jetstar Japan (QF/JL), Jetstar Pacific (QF), Vuelig (BA/IB) are not