Liam moved to NZ in 2004 when he was just 6 which means that when he first played for SA in 2015 he was also eligible for NZ (assuming he has NZ citizenship?) so now he can switch if he wants.
I seem to recall they had not applied for citizenship as Keryn had become ill with his cancer and that seems to preclude one from gaining citizenship on health expense grounds. I may be wrong but at the time I spoke with him and that was something he mentioned as he planned to return to SA and had a pathway mapped out for Liam in SA to start and then overseas.
OK well if that's true and he doesn't have a NZ passport then we can completely forget about him ever playing for NZ then! Shame.