That's what I mean, which is why sometimes it's best not to know in the first place.
When I started my current job, I joined at the same time as this other guy. I found out a while later that he was on a higher salary than me, for whatever reason (quite a bit more, like £4000). But I was fine with it, as the amount I was getting was great, and the other guy had a child to worry about, so I thought nothing of it is.
My mistake was letting my family know, and I ended up having loads of arguments with my fiancée and mother, with them telling me that I needed to demand more money, or look for another job etc. But I didn't want that, as I like this job, and the pay is good enough.
Anyway, I did nothing, and last Christmas we had yearly reviews, and they said that they noticed I was on lower pay compared to everyone else and I got brought up to the same level.
I don't know what my point was any more.