Mike Franks is Gibbs's Gibbs, but who's Rebecca's Gibbs?

Me and my sister, at breakfast this morning...

Sara: Remember the Sweet Valley Twins books? Remember, they were about Jessica and Elizabeth Wakefield, and they were identical twins, and they lived in California, and they both had long blonde hair and blue-green eyes and heart-shaped faces and dimples? Remember?

Rebecca: *resisting the urge to vomit into her cereal*

Sara: What?