One of Elon Musk's baby mamas, Grimes, a.k.a. Claire Boucher, made a legal filing in San Francisco Superior Court Friday that may indicate all is not copacetic between the two parents, who now share three children together.

The details of the filing are not clear, but Grimes filed what's called a "petition to establish parental relationship," and as the Daily Beast reports, such petitions are common when two parents are not married. But this filing comes a month after Grimes posted a since-deleted tweet in which she implied she had been kept from seeing her son — three-year-old X, or X Æ A-Xii, who was born in May 2020.

The tweet was a reply to a post by biographer Walter Isaacson in which he shared photos of the twins that Musk has with another woman, Neuralink executive Shivon Zilis. Per Daily Beast, Grimes' tweet said, "Tell Shivon to unblock me and tell Elon to let me see my son or plz respond to my lawyer. I have never even been allowed to see a photo of these children until this moment, despite the situation utterly ripping my family apart."

The "plz respond to my lawyer" part suggests that there has been some disagreement about custody or something that dates back over a month.

Grimes would soon delete that reply and then post an extended follow-up saying, "I wud prefer to not breathe any more life into this current press cycle but I want to de-escalate the narrative. I spoke with Shivon at length finally, which was long overdue.  This wasn't her fault, plz don't be angry at her!  We respect each other a lot and we're excited to become friends and have the kids grow up together."

Grimes added, "Women are so often pitted against each other."

Zilis replied publicly, saying, "At the end of the day it all ended up for the best! Thank you for taking the time to really connect and understand each other... You’re a total badass and I respect you very much as well. I can’t wait for kiddo play date."

It's not actually clear which of the three children shared by Musk and Grimes is the subject of the legal filing — TMZ speculates it's the youngest, Tau a.k.a. Techno Mechanicus, and that this could be a path toward seeking specific custody rights and child support.

The existence of this third baby, born at a date not shared with the public, was first revealed in Isaacson's book, which was released three weeks ago. In her tweet reply, Grimes said on September 10, "I wish I could show u how cute little Techno is but my priority rn is keeping my babies out of the public eye."

Musk, 52, has been in a relationship with Grimes, 35, since 2018. He now has had a total of 11 children with three different women, one of whom died as an infant.n

Of their relationship, Grimes told Vanity Fair in early 2022, "There’s no real word for it. I would probably refer to him as my boyfriend, but we’re very fluid. We live in separate houses. We’re best friends. We see each other all the time. ... We just have our own thing going on, and I don’t expect other people to understand it."

Related: Now Elon Musk Says SF Supervisor Dean Preston ‘Should Go To Prison’

Top image: Elon Musk and Grimes attend the Heavenly Bodies: Fashion & The Catholic Imagination Costume Institute Gala at The Metropolitan Museum of Art on May 7, 2018 in New York City. (Photo by Jason Kempin/Getty Images)