Ethan, a product of the Saints Academy, will be returning to Northampton from Worcester Warriors ahead of the start of next season.
It means the Waller siblings will be reunited and once again battle it out for the Saints No.1 shirt.
Alex believes Ethan will offer plenty on his return to Saints and he is looking forward to showing his younger brother what has been built at cinch Stadium at Franklin's Gardens since he left for Worcester in 2017.
"His home is here, he's always been a Northampton fan," Alex said.
"I understand the reasons why he left, and I think most people do, but he always had it in the back of his mind that he wanted to come back.
"I don't want to speak for him, but the ideal plan was probably always that the opportunity to come back would present itself, and it has done.
"He's got a little daughter now and to be able to see her grow up with my kids is great and our mum and dad are around so it's easier babysitting for him rather than him being in Worcester.
"He's not quite had the luxury I've had so we might have to fight over babysitters.
"It's really good to have him back.
"Not only is he a great player but he's a great squad man as well so he'll really add something to this squad.
"He left when the club was in a bit of a downturn and a negative place at times so I'm really looking forward to welcoming him back and showing him what's been built here since Boydy (Saints boss Chris Boyd) took over, and Dows (Phil Dowson) can continue that next season."
For now though, Waller will focus on his bid to help Saints make the Gallagher Premiership play-offs.
The black, green and gold, who are currently eighth in the standings, travel to sixth-placed London Irish on Saturday.
And Waller said: "I love being able to play in big games like this.
"For us, if we want to finish top four, we have to be winning these games.
"We set ourselves up nicely with the win against Wasps and I thought the young lads did really well against Sarries at the weekend so hopefully we can take that momentum into this week.
"We know London Irish are dangerous from everywhere on the park.
"They've got an aggressive, gnarly pack and I'm looking forward to that challenge.
"We've got the ability to beat anyone when we click, but it's just about that consistency, and that has been the message through the whole season really.
"I haven't played at their new stadium yet so it will be interesting to see that.
"Teams being at home anywhere you go, there's always a little bit of edge because you want to win at home especially, like we do here.
"The St Patrick's Day game adds to the occasion and it's apparently pretty much sold out for the first time since they've been there so it's great to be part of.
"Hopefully we can rain on their parade a little bit.
"You have to win away, even if it's ugly.
"Every game now is difficult in the Premiership and you can't write any games off.
"Everyone is so competitive and it really is a must-win every week.
"You have to take it week by week and adapt."
Waller recently broke the record for most Premiership appearances by a prop.
And the 32-year-old, who made his Saints debut in 2009, said: "It does feel like a while ago since I first started.
"It was a real honour to get the record and I just love being part of this squad.
"To have been able to have done it so many times is a privilege every time and hopefully there's more to come."