Richie's Castres side kick off their French Championship final against Toulon at 5.30pm while Jonny's Glasgow go head-to-head with Leinster in the RaboDirect PRO12 equivalent in Dublin 45 minutes later, so some frantic channel-hopping lies in store for those who want to follow the fortunes of Scotland's second-row siblings.
But what of the Gray parents? Should they be loyal to Richie, at 24 the elder of the two, or to 20-year-old Jonny, whose relative inexperience at this level might suggest a greater need for support? Or will they do as young Jonny suggests and try to cover both bases. "I don't know," he said when asked about their plans. "Maybe my mum will go one way and my dad the other."
Whatever their destinations, it will be a day of immense pride for the entire clan as the brothers represent the family on two of European rugby's biggest stages. And Jonny is not immune to such sentiments, for the impression at Scotstoun yesterday was that he takes as much pleasure from Richie's achievements as he does from anything he accomplishes himself.
"I'm very proud of my brother," he said firmly. "Throughout my career, throughout my life, he has always been there for me.
"Since he's made it in rugby I've been able to look at him and the work he has put in to get where he is. To be living next to a guy who was doing that - his diet, nutrition, fitness - that first-hand experience of being a professional really helped me.
It helps, of course, when you share the genetic inheritance of a player who, when he burst on the scene a few seasons ago, quickly established himself as the most potent combination of forward power and athleticism that Scotland had produced in years. Yet, if Jonny had to wait in Richie's long shadow as the latter metamorphosed into a superstar of the sport, he has made up for it over a season in which he has moved from the periphery of the Glasgow squad to the centre, picking up three Scotland caps along the way.
The younger Gray sticks to the Glasgow script by saying that his selection for the Leinster match is by no means guaranteed, but it would be a major surprise if the player who has already been hailed as the Rabo Direct PRO12's Young Player of the Year were to be left on the sidelines for the winner-takes-all showdown at the RDS. These days, the question is not whether Jonny will start in a big game, but who will partner him.
"It is building up slowly," he said of the rising excitement in the Glasgow camp as they head for the biggest game of their history. "Everyone knows we need to get our preparations right. It is going to be such a tough game against a world class side. But everyone is pretty calm."
Castres beat Toulon to the French Championship last year, but their final win was dismissed as a freak outcome and few backed them to be in the mix this season. However, a late surge took them to sixth place in the Top14 table, whereupon they rocked French rugby to its foundations by beating Clermont Auvergne in the Stade Marcel Michelin, ending Clermont's astonishing 77-game winning streak at their home ground.
Toulon might have revenge in mind this time round, and there is also the powerful motivation of wanting to bid farewell to Jonny Wilkinson, playing his last-ever game of professional rugby, in victorious style. Leinster, though, will be similarly inspired as they draw down the curtain on the illustrious career of Brian O'Driscoll, Wilkinson's only serious rival as the best player these islands have produced in the past 20 years.
The O'Driscoll factor will play a huge part in creating the emotional backdrop to Saturday's game in Dublin. It is not clear whether it will distract Leinster or drive them on. Jonny - Gray, not Wilkinson - is just happy that he is likely to be part of such a historic occasion.
"Growing up, you get to see these places [like the RDS] in the Heineken Cup and the Celtic League. It's surreal to be playing there against guys like Brian O'Driscoll and Leo Cullen. It will be a special moment if I'm playing. We are all looking forward to it.
"O'Driscoll is an all-time great of the game. He was everybody's hero - for me, as a forward, as well. It will be a special occasion, but we'll just be focused on the game and trying to get a result."
Sean Lamont, the Warriors' 33-year-old, 86-times-capped winger has signed a two-year contract extension that will keep him at Glasgow until 2016. The club has also confirmed that 21-year-old Rory Hughes, also a winger, has agreed a deal for a one-year professional contract, effectively an upgrade of his current status as an elite development player.