They both play the 4. I can also tell you with certainty that even if Justin withdraws his name, he won't be coming here. They're not taking shine away from each other.
Is this based on any info or your guess? From the highlights, Justin seems like more of an interior type scorer, 3.7 3PA vs 6.4 for Julian.
As others have suggested, them playing together would make the two of them a bigger story, not steal spotlight. Twins/brothers on the same team are always a big story, USC right now, the eastern Washington kids earlier on etc