lol Alastor i reckon many a no direction fan girl has attempted humping their life size poster imagining they're shagging their favourite member
Just as an addition.
If they want to find porn, they will find porn.
Better to talk to them about it. Explain the differences and most importantly save yourself some cash by explaining how not to get viruses or ripped off by credit card companies =P
I actually never had "the talk" with my mum and dad.. Although my mum gave me a book on periods and when i got my first serious boyfriend she took me to the GP and we had a little chat about being safe and using condoms as well as the pill but that was it.
Then like the others have said, i told my middle sister and from there on she told my younger sister. Personally I dont think id go into porn with him, theyre going to watch it at some point but what i would do is pass on some good sex ed sites and mention safe sex and STI's.
Admittedly im not a mum myself yet but i dont think i would go into the porn talk as id be moritfied if my mum had done that to me! But just his/partners safety and a little education he can read in his own space without feeling embaressed will make things a lot easier for both of you.