Lillasyster (meaning Little Sister) was formed as Rallypack in 2004, by former LOK members Martin Westerstrand (lead vocals) and Daniel Cordero (bass).

They are also known for their cover versions of R&B star Rihanna's "Umbrella" the same year (2007) and Katy Perry's "Roar" (2014) which became successful.

They participated in Melodifestivalen 2021 with the song "Pretender", qualifying to the second chance round on 6 February 2021.

They returned to Melodifestivalen the following year, entering the 2022 edition with the song "Till Our Days Are Over".

[1] Daniel Cordero left the band in 2011 and Andy Oh'MyGOD has taken the place as bass player now.