Is there a way of hiding your posts on the walls of others from facebook friends?

[tuxedo cat]

I want to post something flirty on the wall of a guy I'm seeing but I have some very nosy relatives as fb friends (they friended me first), and I would rather they didn't see the post as it will inevitably lead to questions.

 

Will all of my friends automatically see whatever I post on the walls of others, even if they are not mutual friends with those people? And if so is there a way of hiding these posts from them?

 

I tried to do a google search but had trouble finding a definitive answer.