I see many body builders. Have very nice muscular bodies. But some have slopping
Shoulders, while other have square shoulders. Is that a genetic, inherited thing.
Or does it have something to do with weight training??

Its mainly a generic gene... but it could have something to do with the way they train or the way they eat... some people with perfect shoulders have had steroids in the past thus delevelping testtosteron(sp)... meaning they mauture quicker and their muscles build quicker...