Mother, 35, and her half-brother lover, 39, murdered their two eldest sons and plotted to kill four more of their children after social workers deemed her 'a loving, caring and competent' parent 
Incestuous couple Sarah Barrass, 35, and her half-brother Brandon Machin, 39, were jailed for life last year for the murder Tristan Barrass, 13, and his brother Blake, 14, at their home in Sheffield.
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