The former bandmates originally started dating in 2001, and remained in a happy relationship until 2006, when they split up for the first time.
The ex-flames controversially reunited again in June this year, with Hannah apparently dumping her then fiancé Adam Thomas for Paul.
A source told The Sun that they got together again because their chemistry was rekindled after the S Club 7 reunion tour, but that now their lives are too different for their relationship to work, with Paul going on tour again soon.
S Club 7 announcing their 2015 'Bring it all back' UK tour in November 2014
'Hannah and Paul had been apart for so many years and their chemistry came straight back on the tour. But they both have different lives now and are doing different things' the source explained.
'Paul is now in The Rocky Horror Show which is about to go on tour, so they decided mutually that they would go their separate ways.'
However, the two remain 'the best of friends' according the source, so maybe there's still hope for fans of this pop romance. Someone who might be not that heartbroken to hear of the spilt is Hannah's former fiancé Adam.
In an interview with The Sun, Adam revealed his ex-fiancée would complain about her former bandmate all the time.
'Hannah moaned to me until she was blue in the face about Paul - she said he was so fat he could hardly dance,' the personal trainer told Sunday People.
'And now she's with him. He'd moved into my bed before it'd got cold - that's the biggest kick in the teeth.'
The blonde bombshell's ex added: 'I'd do anything for that girl. I was so happy. I wanted her to be my wife. I wanted children with her. I saw the rest of my life with her.'