Leiua told Reuters the All Blacks were keen for him to play for them, but choosing Samoa instead gave him the chance of a reunion with the brother he had rarely seen for a decade.
Leiua and his older brother, London Irish flank Ofisa Treviranus, were separated when the latter became a leading light in the Samoan Sevens side and later moved to Europe.
The 24-year-old winger took a different path and was adopted by a New Zealand-based uncle, leading to his change of surname, and relocated close to Wellington to pursue his professional dreams, later joining the city's Super Rugby franchise.
"We have been a long time away from each other and it was definitely a factor for me in deciding where to play," Leiua said in an interview. "We have been separated for a long time and it has been tough to be away from each other."
Leiua travelled to South Africa for this month's four-team Test series and was delighted to link up with his brother again.
"we have had a really good time in South Africa...it's like a family reunion. Playing with my brother has always been a dream."
Leiua made his debut for Samoa in the victory over Scotland in Durban at the start of the competition and played again alongside his brother in the win over Italy a week later that sealed a final match-up with South Africa in Pretoria on Saturday.
They will be alongside one another again in what he admits is a daunting outing which will bring back childhood memories of sitting in front of the television in their home in the Samoan village of Malie.
"We grew up watching the Springboks play on television and they have always been physical and a tough team to beat. It will be an important moment for us.
"The last two weeks have been pretty good, after so long it is good to be involved with the team. I am very happy with my choice."
Leiua believes the current squad is one of the finest Samoan sides in recent memory, and that the future is bright for the team.
"This is probably the best side Samoa have had in ages. We are building slowly towards the World Cup in 2015...that is our target."
At least Leiua and Treviranus do not have the same problem as another set of brothers in the Samoan squad, Census and James Johnston.
Both are props and fighting for one position in the team, a heavyweight battle that older brother Census has so far won.