DP's DS (16), not strictly my DSS as we are not married but DP is the RP and I spend half the week there and have known his DS for 5 years. His DM is variably involved, but his DS doesn't have close relationship with her.
DSS (I'm going to call him for that for ease, not because I am trying to assume anything) has just started his first proper relationship with a girl who has been a friend of his for some time, i.e. its not a bit of a whim. I've told DP he needs to have a conversation with DSS about safe sex and condoms, but DP finds this very difficult. I don't really understand why, but that's the way it is. I have told him to get a grip, but the grip is sadly lacking 
DSS is very sensible and very good at seeing thing from different points of view. I really don't think he would ever pressure his GF into anything she didn't want. He really does think she's the bees knees I don't think he would risk screwing it up.
I want to buy some condoms, give them to DSS and tell him to keep them in case he ever needs them. I would prefer that DP does this, but that suggestion fell on deaf ears. Is it OK for me to do it, or should I butt out? I'm genuinely unsure so all opinions are welcome.