Jessica Biel's younger brother launches tirade on Justin Timberlake

This proves you shouldn’t mix business with family, or your girlfriend's brother in this case.

Jessica Biel’s younger brother, Justin, has released a series of videos slamming Biel’s longtime on-again, off-again boyfriend and the tequila brand he created that Justin worked for.

Justin’s videos rip apart Timberlake's 901 Tequila company, suggesting that the Friends with Benefits star sabotaged it by not promoting it.

According to Fox News reports that in one video, Justin rants "I've been waiting for [Timberlake] to do something with this f**king brand -- make a song about it, put it in a god damn video, hold it up, take some pictures, I don't care -- just do something because we're dying on the motherf**king vine here!"

While sources say that Justin, who stopped working for the tequila brand as recent as last week, departed his business partnership with Timberlake on good terms but the videos suggest otherwise.

A rep for 901 Tequila told TMZ, who first reported the story, "Justin Biel’s video was intended to be one in a series of videos created by 901 Tequila employees (including the brand owner) as part of a larger viral marketing campaign slated for the end of December. It was released prematurely without our knowledge and prior to the final edit.”