The big lock played Premier Grade rugby with Brothers before signing for Queensland Reds and then making the move to Scotland to play for Aberdeen GSFP and then Glasgow.
A popular figure at Glasgow, Nathan, or 'Tree', won international honours at A level and toured with Scotland to North America in 2002.
Nathan moved to Exeter Chiefs near the end of last season and made a big impact as Exeter narrowly missed out on promotion to the Premiership.
Nathan returned to Brisbane at the end of the English season and Brothers are delighted to him back at the club. "After seeing him at only one training run and 15 minutes in a Division One 1st Grade, he has already added that extra professionalism and intesity we like to see around Crosby Park," coach Paul Mills said.