^^^ I got the impression that Malcolm's brother runs his mouth a lot. Over at
his Q&A at EW Online, Probst says "Ah the loved one visit . . . it yields big rewards for at least one Survivor and yes, Malcolm's brother is a charming treat — and a huge Survivor fan to boot!"
So my guess is either that he says something about the gameplay that Malcolm would prefer not get said, he lets everyone in on the fact that Malcolm is a bigger fan than they realized (wouldn't be that shocking, though) or that Malcolm tells him something (strategy? opinions of other survivors?) that he then blurts to everyone.
Now, watch it be none of those.