Greg was Juliette Holliday's husband. After years of IVF, Juliette fell pregnant, but due to a mix up at the sperm bank, she was given the sperm of Jimmy King. Greg could not handle the news when the mix up came to light and he and Juliette split up. Juliette tracked down Jimmy and got him to sign over his rights to her unborn baby. Juliette went into labour at Jimmy's house and gave birth in his living room. Juliette named her son Carl - which was incidentally the name of one of Jimmy's late brothers - and Jimmy bonded with Carl. Carl's birth changed Greg and Juliette's relationship and Greg wanted to give their marriage another go. Juliette allowed Jimmy to say goodbye to baby Carl for good as she wanted Carl to grow up with a mum and one dad, not two dads.
In late 2015, Greg left Juliette again. She struggled looking after Carl alone so handed him to Jimmy to look after whilst he got his life together.