All Black Vaea Fifita has been described as "heartbroken" after his younger half-brother drowned while on a river outing with friends, but family have urged the grieving sports star to remain with the team ahead of next Saturday's Bledisloe Cup match.

Albert John "AJ" Mapa died on July 27 after failing to resurface when he jumped from a bridge into the Provo River, close to his Salt Lake City, United States, home. The 21-year-old's body was found by emergency services three hours later and his funeral will take place in Salt Lake City today.

Mapa's All Black brother, who is part of the squad who is flying to Perth today, didn't want to comment when contacted by the Herald.

But flanker Fifita earlier posted a loving tribute on Instagram to his "lil bro".

Alongside a photo of the brothers and other family members in Tonga for Fifita's December wedding to Hangale Havea, the 27-year-old shared his heartbreak.

"We are struggling to understand why you had to go so young but I know you're in a better place. I'm so glad you made it to my wedding to stand by my side. I miss you so much man. Ofa atu Nia moe famili. RIP MY LIL BRO #ourangel."

View this post on Instagram

I can’t believe that you’re gone little brother😭. It hurts so much. You’ve been called by God to be with him. Although it’s tough and we are struggling to understand why you had to go so young but I know you’re in a better place. I’m so glad you made it to my wedding to stand by my side. I miss you so much man😭😭 Ofa atu Nia moe famili. RIP MY LIL BRO❤️ #ourangel

A post shared by vaea.fifita | Rugby Player (@vaea.fifita) on Jul 27, 2019 at 10:38pm PDT

By late this week the post had received more than 2600 likes and supportive comments from several incumbent and former All Blacks, including Ma'a Nonu, Ngani Laumape, Ardie Savea, as well as former Warrior and fellow Tongan Konrad Hurrell.

Fellow All Black forward Dane Coles wrote, "Big love brother".

All Blacks media manager Joe Locke said they were respecting Fifita's request for privacy so would not say how they were supporting him.

Mapa and Fifita share a father, Maheuliuli Lapota Fifita, and the All Black had been in close contact with his dad since the tragedy, Mapa's mother Lavinia Mapa Lapota Fifita told the Herald on Sunday.

"Vaea has reached out and is heartbroken he couldn't be here with the family, but we understand. I've told my husband to tell him that his family is first, his wife and his children, and he needs to take care of that first . . . and that's important not just for Vaea, but for who he's representing — your country, New Zealand, and even the Tongan people, they're so proud of Vaea and his accomplishments.

"That's more important than for him to come here. We know he loves us and we know where his heart is and that's what matters to us."

They had told Fifita to "play hard" and keep following his dreams "because AJ is gone, he'll never be forgotten, but Vaea has a family to support and a country who counts on him".

AJ was the youngest of her husband's seven children, and their only child together, and first met his older half-siblings at Fifita's wedding in Tonga in December. The other half-siblings also included Leva Fifita, a Tongan rugby international who previously played for Waikato in the Mitre 10 Cup and is now with Grenoble, in France.

Her son was "starstruck" by his All Black older brother, Lavinia Fifita said.

"He's always wanted to meet his family, so that was a big deal for him to meet Vaea. And he was starstruck, you know, to know the position Vaea was, and even his older brother Leva.

"Once they got to meet each other it was like any other siblings. Vaea totally took him in, and the other siblings too. It was a good reunion, it was like a family reunion for my husband's children."

Following the wedding, Fifita posted a thank you on Instagram to friends and family who had shared his special day.

"I would like to thank everyone that turned up and made our day . . . it'll never be forgotten," Fifita wrote.

AJ, who was born and raised in the United States, was a "fun, loving and happy" person who "always made sure everyone else was good", Lavinia Fifita said.

He had spent time overseas as a missionary, planned to marry his girlfriend, had a job and was starting university — with a long-term goal to study engineering — in September.

As a child he played football and baseball, switching to basketball as a teenager, and he wasn't immediately aware of his half-brother's success with the Hurricanes and the All Blacks.

"[But] when everyone else talked about it, I think there might've been something he saw online, I'm not too sure, and yeah he was proud, he was totally ecstatic and happy and stood a little bit taller knowing that Vaea was his brother."

But Fifita had acted in a way that ensured AJ knew he was "a brother first".

"Forget about what his stature is or where he plays. The way they interacted with each other at the wedding, it was two brothers meeting and getting to know each other.

"I think that's [because of] the warmth that radiates from Vaea. He's a totally down to earth guy ... [for three half-siblings] it was the first time they met Vaea. It was a big deal for them, but Vaea made sure that he really was around to spend as much time as he could.

"It was his wedding, there was a lot of family members, but he did take it out of his time to make sure those three were taken care of and he spent as much time as he could with them."

The family were together for three days, she said.

"It was a very short time, but it was time that counted. That's the most important thing."