Danny Riordan, an aspiring songwriter and friend of the Raisens who said he was present for part of the “Healthy” session, remembered the excitement in the room as the song boomed over the studio speakers.

“Everyone was like, ‘Oh my God, this is going to be huge,’” Riordan said.

Five months after the session that produced “Healthy,” “Truth Hurts” was released, and the Raisens said they were surprised that Lizzo’s song contained the “DNA test” line but without credit given to them or Rothman.

“There was a bittersweet emotion, because deep in our hearts we know that we were a part of this song,” Jeremiah Raisen said. “We should feel validated but we’re not.”

The Raisens said they began their campaign shortly after, seeking 5 percent each of the songwriting royalties from “Truth Hurts.” As the song climbed to No. 1 this summer, the brothers took up something of a vigilante campaign on social media, posting congratulatory messages to Lizzo while also aggressively arguing their case.

But the Raisens’ case may be complicated by the fact that they rescinded an earlier claim over “Truth Hurts” through their publisher, Kobalt, which Lizzo’s representatives believe should bar them from pursuing the matter further.

Lizzo’s representatives do not contest that the session yielded “Healthy” and its “DNA test” line. The crux of the disagreement is who did what: The brothers say the session was conducted with the understanding that all parties were contributing to the resulting work, and that Lizzo’s vocal was tailored to the instrumental track they created. Lizzo’s representatives say the Raisens were not involved in creating Lizzo’s vocal line and so have no claim to it now.