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While working on a school geneology project, Ben (Jeremy Miller)) uncovers a startling secret: his dad Jason (Alan Thicke) was previously married and divorced before wedding Ben's mom Maggie (Joanna Kerns)! Armed with this shocking knowledge, Ben, Mike (Kirk Cameron) and Carol (Tracey Gold) do some additional burrowing into the Seaver family catacombs to find out if they have any heretofore unacknowledged half-siblings lurking throughout the world. This leads them to expose still another shocker: Maggie was likewise married before she met Jason!