Paul Cattermole says he was forced to date Hannah Spearritt for a TV show as he claimed it was "written into their TV contracts".
The star claimed that his relationship with Hannah was part of the deal after appearing on the show Hollywood 7, which is a spin-off of the band's CBBC show Miami 7.
Paul told the Guardian's G2 supplement that the relationship "did not happen organically", and that it had been "written into the Hollywood 7 show".
He added: "And because of that, it sort of happened."
The 42-year-old was asked if he "felt forced into the relationship, in which he replied: "Yeah, but like I say. It didn't feel like that because I had totally grown into the idea, quite quickly...I thought she was great."
The pair split up in 2006, but then got back together for a few months later in 2015, although Paul denied that he and Hannah were dating at the time the show aired.
Shortly after, they then called time on their relationship for good.
The show Miami 7 was getting around 90m viewers around the world when it was first aired in 1999.
It was the same year that the band's first single Bring It All Back went to No1 in the UK charts.
The band starred in Hollywood 7 in the third series of the show back in October 2001, where Paul and Hannah kissed for the first time on screen on the fifth episode called The Kiss.
He also told the Guardian he was up for a "reunion tour" to celebrate the 20th anniversary of their debut album, but he said it was "unlikely to happen".
Paul said: "The other guys know I'm up for doing it, but I don't know what's happening."
Cattermole left the band in 2002 to form his own band Skua, and S Club 7 split the following year.
