'Welcome to Sweetie Pie's' Owner Charged with Conspiracy in Nephew's Murder

"Welcome to Sweetie Pie's" star Miss Robbie is dealing with a new family shocker tied to the murder of her grandson -- cops have arrested her own son for an alleged murder-for-hire plot straight outta "Dateline."

Miss Robbie's son, and costar on the OWN show, James Timothy Norman was busted by feds for his alleged role in the 2016 shooting death of Andre Montgomery ... his nephew and Miss Robbie's grandchild.

According to docs, prosecutors say Norman -- who owns Sweetie Pie's restaurant -- took out a $450k life insurance policy on his nephew back in 2014 ... and then worked with a woman named Terica Ellis to allegedly pull off the murder. The feds claim they communicated on burner phones in the days leading up to the killing in St. Louis.

In docs, obtained by TMZ, prosecutors claim Ellis got Andre's location the day of the murder ... then placed a call to Norman. Shortly after that, on March 14, 2016 ... Montgomery was shot at killed, and the feds claim they ping'd Ellis' phone near the scene of the crime.

Immediately after Montgomery's murder ... Ellis allegedly called Norman, left town and deposited $9k in cash into various bank accounts. Prosecutors say Norman then contacted the life insurance company in an attempt to collect on the policy.

Ellis is facing the same murder-for-hire conspiracy charge as Norman.