By Alex Lowe, Press Association Sport England Rugby Union Correspondent
Wasps number eight Billy Vunipola is bracing himself for an “awkward” weekend as he prepares to play against his elder brother, the Saracens and England prop Mako, for the first time in anger.
The only other occasion they have found themselves on the opposite sides of a ruck was in a trial match of three periods for Bristol, when Billy was still at Castle School.
On that day, Billy did his best to avoid any direct confrontation with Mako and he has admitted the same will be the case at Adams Park on Saturday.
"In the last period of that trial, Mako and I were put up against each other. We ran into a ruck together and he told me to go and stand on the opposite side of the pitch so we could avoid each other," Vunipola told Press Association Sport.
"Being the younger brother I did it. Even though I was playing back row I spent most of my time on the wing.
"It is a weird feeling coming up against your older sibling. It is hard to say this but when he runs at me I don’t think I will try and hit him as hard as I will hit other people.
"If he runs at me I will do a job for my team and I will try and stop him but there is something deep inside that just says it is not right to go out and hurt my brother.
"It will be pretty awkward for me and for my family."
Awkward is a word that crops up a great deal in conversation with Vunipola, much of it down to the culture clash between his Tongan upbringing and life as an English professional player.
On Saturday, Vunipola will be anxious to preserve familial harmony but also desperate to prove to Wasps how grateful he is for giving him a start in professional rugby.
That family-versus-club dichotomy goes right to the heart of Vunipola’s decision to leave Wasps at the end of the season and join Mako at Saracens.
It was an agonising call for Vunipola, who felt he was betraying the club who had developed him from an overweight teenager to the brink of England honours.
Ultimately, Vunipola’s family ties - so important in the Tongan culture from which he descends - proved too strong. It was his family’s wish and so he acceded.
"If I play for England then all of the credit goes to Wasps. I can’t emphasise how much this club has done for me and how much it means to me," Vunipola said.
"I am not here for much longer. I am just trying my best for everyone at the club.
"There are other reasons why I am leaving. It is for my family. I tried to fight it but it is how we are brought up. It is what felt right for everyone around at home.
"We are really close. It is going to be so awkward on Saturday and that is the biggest thing, the split of who to support. Playing with my brother would help my family out in ways Wasps couldn’t."
Uniting the brothers at Saracens was the wish of their father Fe’a, the former Tongan captain who brought his family to the UK in 1999 when he signed for Pontypool.
Wasps were angry with the way the family handled the move. A deal was done with Saracens while Wasps were still under the impression Vunipola was staying with them.
"When it came up, I felt really awkward around here at Wasps. I couldn’t really look the boys in the eye," Vunipola said.
"It felt like I had let my friends down, the whole team. It took about a week before everything died down.
"My Dad suggested it. I knew if I stayed at Wasps then it would be awkward at home for a while.
"In Tonga it is still the old-fashioned culture of what the parents say goes. It is tough to maybe think about it in today’s culture, where people can do what they want when they are 18.
"Back home, religion is still number one and your parents are the boss. My brother and I firmly believe that.
"It was disciplined and hard at times when your friends are out and you have to stay in and do your homework and do the chores.
"But we were lucky we had rugby. That was so big for us. It was an outlet."
Vunipola played four years above his age-group when he was at school in Bristol and he was recruited by Wasps after winning a sports scholarship to Harrow School.
After playing an influential role in Wasps’ survival last season, Vunipola made a sensational start to this campaign and he was fast-tracked into the England squad for the RBS 6 Nations.
Even that was an awkward experience, initially, because he turned up to camp unable to train having injured his ankle playing for Wasps.
"I imagined the others saying ‘here’s the new guy and he’s not even training, he’s just here for the free food’," Vunipola laughed.
England badly missed the presence of a dynamic, ball-carrying number eight after Ben Morgan was injured but a different ankle problem denied Vunipola the chance of a Test debut against France.
That will surely now come on the summer tour of Argentina. England head coach Stuart Lancaster is desperate to get Vunipola involved at Test level.
"It wasn’t my time," said Vunipola, who has seen Mako flourish since making his own Test debut in the autumn.
"Mako has had a taste of the big time with England and he wants more of it. He is pushing himself and it is showing in his performances.
"He’s doing awesome."