Because not only does he get to spend more time with his sibling, but he also gets an extra babysitter and cook at his house.
"He's living with me and he's on uncle duties and cooking duties," Sam said, laughing.
"I was very lucky because I got to present him his first shirt, which was awesome and a bit emotional as well.
"Last year he was playing in National 2 but now he's made the jump and he's slotted in really well.
"No one really asked me about him but he became available, they needed a bit of cover for the Six Nations and he's come in and done really well and he's here to the end of the season."
Not so long ago, Joel was working on a building site, but now his focus is on building a career at Saints.
The Matavesi brothers clearly have plenty of talent, with centre Joel and hooker Sam at Saints and utility back Josh currently playing in Japan at Toyota Industries Shuttles Aichi.
Sam said: "Josh loves it. He's in Japan currently and with the time difference and stuff he's always looking for links for the games.
"At Newcastle and Ospreys before that, those boys were together, so I was always the odd one out.
"Now me and Joel are living together and it's nice to have him around.
"He loves it here and he's fitted straight in. The boys have been awesome.
"It's good that we play in very different positions and he can be himself.
"The coaching has been really good for him, he's had good feedback and he's loved the link with Bedford.
"It's been awesome for him.
"You've got to put in a lot of work because this is a different lifestyle in terms of food and recovery.
"Not only that, he's got to show a bit of want in the sessions and the speed of National 2 is a lot different to the Prem.
"He's getting to grips with it and hopefully he gets a contract off the back of it."
Sam also arrived at Saints on a short-term contract, back in December 2019, but he's since become first-choice in the No.2 shirt.
So what advice does he give his brother as he bids to stick around at cinch Stadium at Franklin's Gardens beyond the current season?
"Have no regrets and don't be at the back," Sam said.
"If you get things wrong, get things wrong, but have a go."
That has certainly worked for Sam, who is set to play his 50th game for Saints, at Bath on Saturday.
"It's my 50th game this week and I wouldn't have expected that when I first came here for six months," Sam said.
"You've got to have that inner belief and desire.
"I like to think I've come out of my shell a bit more, got a bit more confidence in the group.
"It's been unbelievable but I don't just want it to be last year and this year. I want 100 games, 150 games.
"I need to find the next level of what I can do now."
Sam will hope to do that in the next few weeks as he bids to help Saints secure a top-four spot in the Gallagher Premiership.
"It's what we want - it's knockout rugby again," he said.
"We've got a few massive games coming up and we want to be playing the top teams.
"We want to be in the top four and it's a massive opportunity for us."
Saints will look to enhance their play-off hopes by beating bottom side Bath at The Rec this weekend.
But the black, green and gold do not have a good record at the ground, having failed to win at The Rec since December 2015.
And they know they will have a tough task on their hands against a Bath team packed with talented players.
"They're a great team individually," Sam said.
"Their captain came out and said they've got a lot of great individuals but they're just not clicking.
"We don't want it to click this week against us.
"If they get it right, they're going to be a very dangerous team.
"Our job is to start well and keep the pressure on them.
"The messages we've got from the coaches this week is that we haven't got to pull rabbits out of hats, we've just got to be on our game physically and be better at the breakdown.
"We can do it but we need to keep backing it up and show some consistency. If we can do that, we can be in the top four."