The young full-backs moved to Old Trafford from Fluminense in January 2008 when they were just 17-years-old.
They have both gone on to force their way into Sir Alex Ferguson's first-team squad, though the Scot elected to send Fabio on-loan to QPR at the start of this season.
The move not only allowed the pair, now 22, to play more first-team football but also become more independent and mature.
Rafael concedes that he misses his brother, currently sidelined with a hamstring injury, but accepts that the deal is good for both their development.
"It's not strange but it's different," he told the club's official website. "We're close and I was always together with him but it's been good for us, just to become more mature.
"I used to ask him all the time if I needed something but now I need more of my own mind so I've grown more mature. It's bad because I miss him but it's good to learn more.
"He is always calling me back to say something is not good [about my game].
"It's always been like this. He is back in training now and maybe, when he plays again, we'll keep doing this."