In a post-apocalyptic wasteland, when a government transporter with a death-wish learns that his long dead brother is alive he teams up with an escaped experimental super-soldier and a sassy resistance fighter to find his lost brother and stop a deranged government scientist who is experimenting on children.

Yeah, they are one and the same. The brother is in the experiment. Thanks for the info.

Just rearrange and streamline, and I think you'll be able to sort it out.

"After learning his long lost brother is alive (or, is held captive by a sadistic scientist ... is his brother young enough to be one of the experiments?), a (reckless?) government agent travels across a post apocalyptic wasteland to mount a rescue."

Because there are two goals - save the brother, stop the scientist - the second half of the logline gets muddled. If they tie in directly to one another, make that clear. If not, which is the goal that, once completed, finishes your movie?

Yeah, I know.. I guess the first thing I'd ask is if you feel I need to setup the 'world' at all.. The first four words are wasted on this and while I feel it's very important because it's not the same story if it takes place in present day America, it also bogs down the logline from the get go.