The whole question seems odd to me.  We're talking about a 15 year old who likely has seen more porn already than many of us even know exists -- unless of course he lives in a very strict household.

If, on the other hand, the OP is really just concerned that her brother might make some nudie pictures which the parents may find and get upset about, the only issue is whether or not her brother has his own machine and whether or not the folks snoop on it.  If they do, and they are the sort who would have seizures at the thought of a 15 year old thinking about porn, then I'd steer him toward Daz Studio.  I find it hard to imagine any normal 15 year old (girl or boy) not being curious about the erotic potential of a 3d rendering program.  But maybe kids today are just way more uptight than I think.

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