Miley Cyrus flirts with sister's boyfriend? Teen twerker 'tries to sleep' with Brandi Cyrus' rocker BF Sam Hancock, ignites family feud?

Want to know what's "tearing Miley Cyrus' family apart?"

Apparently, the Bangerz songstress tried to flirt with her very own sister's boyfriend a few years ago!

A recent cover issue of Life & Style magazine blares the seedy headline:

"She tried to seduce her sister's a boyfriend: a new low! Miley's so desperate for attention that nothing is off-limits anymore - not even betraying her own sister. Inside the fight that's tearing the family apart."

Funny thing is - this allegedly happened back in 2008-2010, when Cyrus was still a "teen." Apparently, the infamous twerker tried to "make a move" on her older sister Brandi Cyrus' leading man (at the time), Christian rocker Sam Hancock.

An alleged magazine insider reveals that "she was trying to hook up with him and date him."

The source continues, "She was basically trying to steal her sister's boyfriend, or at least cheat with him... Brandi would always complain about Miley hitting on her boyfriend."

Apparently, some tabloids are digging for freshly "controversial" Miley news. But seriously - this "flirtation" allegedly happened over four years ago!

Hancock even told Life & Style, the "Wrecking Ball" songstress "was nothing more than a little sister to me."

Another rep tells Gossip Cop that this new report is totally "ridiculous" and "completely fabricated." Cyrus did not "ruin" her relationship with Brandi over a silly ex-boyfriend.