Ed Sheeran is one of the most successful singer-songwriters working in the pop music industry today. He’s also been repeatedly sued for copyright infringement. He had to give up part ownership of “Photograph” last year to settle one lawsuit. He’s also facing pending litigation over a song he penned for Tim McGraw and Faith Hill. But in terms of sheer oddness, that’s nothing compared to what’s going on over Sheeran’s “Thinking Out Loud,” alleged to be a rip-off of the Marvin Gaye classic “Let’s Get It On.”

“Let’s Get It On,” released in 1973, was co-written by Ed Townsend Jr., whose “heirs” are now pursuing copyright claims against Sheeran and associated music companies. And yes, there’s a reason for the use of quotation marks, as this legal battle has recently introduced paternity and the guy who invented “Bowie bonds,” among other things.

We’ll start on the latter topic since a new lawsuit filed on Thursday is getting attention without the really interesting context.

Back in May, an entity called Structured Asset Sales wrote a letter to the New York judge seeking permission to become an additional co-plaintiff in the case over “Thinking Out Loud.”

Represented by attorney Hillel Parness, who was once the head of litigation at Warner Music, Structured Asset Sales was founded by investment banker David Pullman, who made a splash in the late 1990s by securitizing future royalties to musical intellectual property and then selling these asset-backed securities to other investors. David Bowie was just one of many musicians who decided to sell off future income in exchange for money upfront. Other securitized works included songs from James Brown and the Isley Brothers.

Structured Asset Sales apparently made a deal with one of Ed Townsend Jr.’s children, Clef Michael Townsend, and alleges owning a piece of “Let’s Get It On.” As either the part owner of the song’s copyright or a beneficial owner of proceeds from the song, Pullman’s company asserts a stake in the litigation.

Nevertheless, US District Judge Richard Sullivan on 6/11 rejected the motion for intervention because he said it was “clearly untimely.” In his decision, Sullivan pointed out how the case over “Thinking Out Loud” was a “widely publicized action,” with great press attention, and yet Structured Asset Sales had waited about two years until discovery was closed in a bid to become involved.

Pullman’s company is now appealing up to the 2nd Circuit, but in the meantime, Structured Asset Sales filed a new lawsuit today that basically repeats the claim that “Thinking Out Loud” is a copyright infringement of “Let’s Get It On.”

The alleged infringement will of course be tested on summary judgment in the first case (or technically, the second case, as Townsend’s heirs had to sue twice after initially failing to serve papers on defendants).

Typically, what’s most important at this stage is the musicologists weighing in on similarities between the respective songs as well as depositions from those involved in creating the music. And while this case has plenty of that — plaintiffs point out that Sheeran segued “Let’s Get It On” with “Thinking Out Loud” in performances, nod to correspondence between Sheeran and his manager about the similarities and fight defendants’ contentions about unprotectable elements like common song structures and percussive rhythms — Judge Sullivan will have even more to think about this time.

One of Townsend’s children and a co-plaintiff in this lawsuit is Kathy Griffin (not the comedian). Sheeran’s camp is challenging her standing because they say she “was adopted by others at birth and under California law of intestate succession, she has no right to succeed to Mr. Townsend’s interest in the song.”

A letter to the judge on Wednesday by Pryor Cashman attorney Donald Zakarin, representing the defendants and outlining coming summary judgment papers, goes even further in explaining the challenge.

“Kathryn’s lack of standing due to her adoption was first confirmed at her deposition dated April 24, 2017,” writes Zakarin. “Based largely on hearsay, Kathryn testified as follows: (a) while she believes Townsend is her biological father, no DNA or paternity testing was performed (and Plaintiffs have failed and refused to produce Kathryn’s birth certificate), (b) Townsend supposedly conceived Kathryn with an unknown woman of the Catholic faith who refused to raise her, (c) the physician who delivered Kathryn supposedly cared for Kathryn during the first few months of her life (which sounds improbable at best) until Shirley and Earnest Griffin adopted Kathryn and moved with her to Mississippi, where they raised her until she reached the age of majority, and (d) Kathryn was approximately 26 years old when she first learned that she had been adopted and that Townsend allegedly was her biological father.”

The attorney for the plaintiffs argues that Griffin was determined to be a lawful heir a decade ago by a probate court and was awarded an interest in Townsend’s music catalogue. The plaintiffs add that Sony/ATV — one of the co-defendants — has been paying Griffin royalties on “Let’s Get It On” through that time without any objection.

Zakarin responds that defendants examined California probate court records to investigate and came to the conclusion that heirs withheld information a decade ago and thus “tainted” the determination.

“In particular, plaintiff Helen McDonald, who initially served as the ‘Personal Representative’ of Townsend’s estate in the probate proceedings, concealed Kathryn’s adoption from the Court,” he writes. “In fact, she specifically represented to the Court that Kathryn had not been adopted.”

Zakarin adds that Jobete Music — not Sony — administers rights to “Let’s Get It On” and has been paying royalties based on information provided by McDonald and Griffin and represented as accurate.

In sum, the dispute over whether Marvin Gaye’s most iconic songs has been infringed and has become something extraordinary. An investment banker with alleged beneficial ownership is coming forward with his own claims while the supposed “Let’s Get It On” inheritance by one of the songwriter’s biological children is being doubted — all this emanating from a celebration of lovemaking.

This article originally appeared on The Hollywood Reporter.