Being seven years the older didn't give him any advantage when it came to Sherlock.
He could still remember the first time he saw him – a tiny baby with a mop of black curls, eerily quiet for a newborn. He neither liked nor disliked him; Mycroft didn't care about such things, he merely filed away the details for future reference.
(Like the hushed words he caught once – borderline Asperger syndrome, that's what a doctor said.)
The two of them never really got along, but Sherlock seemed to do with that John fellow now.
It was a relief in a way.