11:05 AM PT -- Mark and Tina tell TMZ, "At first we thought this comical legal document was a parody. Instead, this so-called lawsuit by the brothers is more of their lawyer driven nonsense, and a desperate attempt for them to stay relevant and further profit from an attack they admit they perpetrated."

They continue, "While we know this ridiculous lawsuit will soon be dismissed because it lacks any legal footing, we look forward to exposing the fraud the Osundairo brothers and their attorneys have committed on the public."

9:43 AM PT -- Ola was out and about Monday afternoon in Chicago ... looking carefree a day before he his brother, Abel, filed a lawsuit in federal court. Ola's asked if he thinks Jussie owes the City of Chicago an apology. He seems more psyched hanging out with his boy and their exotic pets.

8:35 AM PT -- The presser just ended and NOBODY asked why Abel and Ola are NOT suing Jussie. The brothers' attorney, Gloria Schmidt, read a statement on behalf of the brothers ... saying they can no longer sit back and watch lie after lie being fabricated about them.

7:45 AM PT -- The brothers' attorneys are holding a news conference in Chicago, and we'll be live streaming. The big question, of course ... WHY didn't Abel and Ola sue Jussie Smollett???

The 2 brothers who allegedly faked the Jussie Smollett attack are suing the actor's lawyers, Mark Geragos and Tina Glandian, for defamation, claiming the attorneys lied to the media and tried to make it appear Ola and Abel Osundairo were the culprits in a real, homophobic and racist attack.

The brothers filed the case in Chicago federal court, claiming Jussie "used his clout as a wealthy actor to influence [the brothers] who were in a subordinate relationship to him and were aspiring to 'make it.'"

The suit says when Tina Glandian went on 'GMA,' "Today" and the Reasonable Doubt podcast after the charges against Jussie were dismissed, she told a string of lies ... including the brothers wore whiteface during the attack and the brothers were involved in an illegal Nigerian steroid trafficking ring.

The lawsuit also claims Glandian falsely claimed one of the brothers "engaged in fornication with Mr. Smollett."

As for Geragos, the suit claims he "repeatedly indicated that plaintiffs conspired to criminally attack Mr. Smollett, and by doing so, implied plaintiffs committed perjury" to the Grand Jury and conspired to make false statements to the Chicago PD.

The suit doubles down and says the brothers never knew Jussie would go to the cops ... rather, he was staging the "attack" for social media.

The brothers say as a result of the alleged defamation they suffered extreme emotional distress, humiliation, anxiety, damages to their reputation, and damages to current and prospective business relations.

As we reported, Ola and Abel have had a tough time finding work, both as actors and personal trainers, in the wake of the scandal.

One final thing ... it's interesting the brothers did not sue Jussie, who also claimed they were the culprits in the alleged racist and homophobic attack.