In February 1999, „The Animal Song”, which was featured in the Touchstone film The Other Sister, became a No. 3 hit in Australia and Top 20 in the UK and US. In September they released „I Knew I Loved You” – a love ballad – which peaked at No. 4 in Australia and No. 10 in the UK. It was followed in November by the duo’s second album, Affirmation, produced by Walter Afanasieff (Ricky Martin, Mariah Carey, Celine Dion). Described by McFarlane as „pure unadulterated pop, boasting enticing melodies and a classy and sleek production sound”. The album peaked at No. 1 in Australia and eventually achieved 8× platinum. Within a month it went platinum in the US, partly due to the success of the single „I Knew I Loved You”, which hit No. 1 on the Hot 100, subsequently going platinum and becoming the most-played single on US radio for the year.