Lee Johnson was victorious in the Johnson versus Johnson clash at Boundary Park.
Lee's Oldham Athletic side beat his father Gary's Yeovil Town team 1-0 after a goal by Matt Smith on the stroke of half-time.
Oldham's win sends Portsmouth and Hartlepool down to League Two and moves the Latics further away from the relegation zone.
Yeovil's defeat dents their hopes of winning automatic promotion, but they are still guaranteed a play-off place.
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