Who knew a simple T-shirt could wreck such havoc?

Gronk Nation LLC is a charitable corporation run by New England Patriots star tight end Rob Gronkowski and his fellow NFL-playing brothers, Dan and Chris.

Sully’s Tees LLC is a Peabody, Massachusetts, merchandise manufacturer specializing in the sales of apparel celebrating Boston sports.

Gronk Nation sued Sully’s in 2013 for trademark infringement after learning that the company was selling shirts sporting Rob’s likeness and slogans such as “Gronk” and “You Got Gronk’d.”

“There is no justification to using one’s name or likeness to profit without the person’s permission, particularly where it is a person who has gained some form of notoriety, which Rob Gronkowski has certainly done in this jurisdiction,” Gronk Nation’s lawyer, Timothy J. Perry of Boston, said at the time.

Sully’s Tees countered with a motion to dismiss the federal lawsuit, arguing that it started selling its Gronk products before the Gronkowskis assigned intellectual property rights in their names, nicknames, images, pictures, likenesses and trademarks to Gronk Nation.

“This is fatal to Gronk Nation’s claims under the well-established trademark principle that ‘first in time equals first in right,’” Sully’s Tees’ Foley & Lardner lawyers, Matthew B. Lowrie and Lucas I. Silva of Boston, wrote.

U.S. District Court Judge F. Dennis Saylor IV denied the motion to dismiss in April 2014.

“The complaint alleges that defendant’s use of GRONK on t-shirts has created a likelihood of confusion that the Gronkowski brothers or Gronk Nation are associated with or have approved its merchandise. This suffices to state a claim under Section 43(a) [of the Lanham Act],” Saylor wrote. “Whether defendant used the mark on t-shirts prior to the date of first use listed on plaintiff’s trademark registration is not the critical inquiry. A trademark does not have to be registered to be protected under the Lanham Act. … The registration itself is only prima facie evidence of a valid trademark. And the ‘good’ in a false endorsement claim is not a particular product but instead the celebrity’s persona and goodwill.”

Quick on the heels of Saylor’s ruling, the defense filed an answer to the lawsuit and countersued for trademark cancellation “and unfair competition and deception arising under state statutes and common law.”

“Counterclaim Defendant … engaged in unfair competition and unfair and deceptive trade practices under Chapter 93A by filing one or more trademark or service mark applications with the United States Patent and Trademark Office with knowledge of Sully’s prior use described herein,” the filing states. “Counterclaim Defendant did not disclose Sully’s prior use to the United States Patent and Trademark Office at the time it prosecuted any of the … Registrations.”

The case was reassigned to U.S. District Court Judge Indira Talwani in Boston last June.

In September, the parties quietly settled and entered a stipulation of dismissal. Each party bore its own costs and attorneys’ fees. Other terms of the settlement have not been disclosed, and the attorneys involved in the case did not returned messages seeking comment.

Perry previously indicated that any money Gronk Nation recovered through legal action would be donated to the Gronk Nation Youth Foundation.