Complex sentence: Gabriel arrived in the series in 2003 and was immediately at the centre of controversy when he seduced Sgt. June Ackland only to produce his adopted brother Gabriel's birth certificate claiming it was his and that he was the son she had given up for adoption.
Split into simpler sentences: Gabriel arrived in the series in 2003 and was immediately at the centre of controversy when he seduced Sgt. June Ackland. He then produced his adopted brother Gabriel's birth certificate claiming it was his and that he was the son she had given up for adoption.