The genera Polypompholyx (two species of pink petticoats or fairy aprons) and Biovularia were formerly regarded as fourth and fifth members of this family. Biovularia has been subsumed into Utricularia, and Polypompholyx has been relegated to a subgenus of Utricularia. Placement of the family was previously in the Scrophulariales, which has been merged with Lamiales in the Angiosperm Phylogeny Group system.
References
Jobson, Richard W., Playford, Julia, Cameron, Kenneth M. and Albert, Victor A. (2003). "Molecular Phylogenetics of Lentibulariaceae Inferred from Plastid rps16 Intron and trnL-F DNA Sequences: Implications for Character Evolution and Biogeography". Systematic Botany28: 157–171. (abstract here).
K. Müller, T. Borsch, L. Legendre, S. Porembski, I. Theisen and W. Barthlott (2004). "Evolution of Carnivory in Lentibulariaceae and the Lamiales". Plant Biology (Stuttgart)6: 477–490. doi:10.1055/s-2004-817909. (abstract here).