DOES THE BRO CODE ALSO APPLY TO FUCK RELATIONSHIPS?

Every guy knows this golden rule: You don't fuck your best friend's girlfriend! But does that actually apply to a fuck relationship as well? In any case, the best buddy of my F+ friendship helped me renovate my apartment. If only he didn't look so horny and walk around my apartment topless all the time... But like I said, best buddy just.... Will he stick to the agreed bro code???