One who hugs, kisses or has close physical contact with those they may not marry (except for one's children and parents), deserves 39 lashes by Bet Din, and is considered to be suspect of being promiscuous.
One is not allowed to seclude oneself with those one may not marry (except for one's children and parents), a prohibition known as Yichud.
Applies to everybody, everywhere, always
Verse: "None of you shall approach anybody who is near of kin to him" (Vayikra 18:6)
Source: The Chafetz-Chaim's Sefer haMitzvot haKatzar; Prohibition 110
Sunday, 24 Sivan 5770