Don’t get Rob Lowe mad — or try to blackmail him. He will fight back. Rob Lowe, who co-stars on “Brothers & Sisters,” is suing two ex-nannies and a former chef for a variety of wrong-doings. Go Rob!

First, one of the former nannies tried to extort $1.5 million from him and his wife — and Rob Lowe made the nanny’s intentions very public yesterday, saying she was making an “attempt to damage and humiliate” his family.

And, in the three separate lawsuits he’s filed (against each of the two former nannies and a former chef), Rob Lowe claims they had sex on his bed “with third parties” and stole prescription drugs. In all, Rob Lowe’s lawsuit accuses the employees of “breach of contract, defamation and intentional infliction of emotional distress.”

Rob Lowe’s complaint against the nanny included the woman claiming to have “a personal and intimate relationship (with Lowe), and, in effect, accusing Rob Lowe of infidelity.” The nanny also claims that Rob Lowe sexually harassed her and that his wife was an “overly demanding” and “abusive” employer, who made “inappropriate comments of a sexual and racial nature” to her.