Serena and Meghan
Is Serena Williams cashing in on Meghan Markle? Pictured: Hannah Davis, Nina Agdal, Serena Williams, Meghan Markle and Shay Mitchell participate in DirecTV Beach Bowl at Pier 40 on Feb. 1, 2014 in New York City. Getty Images/Michael Loccisano

Meghan Markle's good friend Serena Williams may be taking advantage of the Meghan Effect.

Emily Chan of Daily Mail recently questioned the timing of the release of Williams' Royal Duchess hoodie. The athlete unveiled the $90 jacket inspired by the Duchess of Sussex. Wiliams also revealed that she sent one to Kensington Palace.

The tennis player posted a photo of the hoodie on Instagram. "Queen + Queen = ROyal. Me and @nickiminaj having fun with boomerang. Wearing the royal hoodie by @Serena. Link in bio!" she wrote in the caption.

Williams' Royal Duchess cropped hoodie is available in black and blue colors. It's part of her clothing line.

Williams and Markle have been good friends for years. Their friendship started in February 2014 when both had to play a game of flag football on DirecTV's Celebrity Beach Bowl. The pair immediately hit it off. In fact, Prince Harry's wife even called Williams her "confidante."

"She quickly became a confidante I would text when I was traveling, the friend I would rally around for her tennis matches, and the down to earth chick I was able to grab lunch with just a couple weeks ago in Toronto," Markle wrote about Williams on her blog, The Tig.

In September 2016, Williams graced the runway at New York Fashion Week and the former "Suits" star was there to support her. In fact, Markle, who was still very active on Instagram at that time, posted a photo of them together.

"My eyes are closed but my heart is so open! So proud of your new collection @serenawilliams Happy I could be there to support you xx #NYFW," she wrote.

Williams is among Prince Harry and Markle's celebrity guests during their royal wedding in May. The athlete arrived with her husband, Alexis Ohanian.

In July, Williams and Markle were spotted together watching Audi Polo Cup. It was the first time the two were seen together following Markle's wedding.

In related news, although Williams is close to Markle, she considered her sister-in-law Kate Middleton the toughest woman she knows. "Well, obviously Beyoncé. That goes unsaid. Rihanna goes unsaid. Kate Middleton!" Williams said about the royal mom of three.

According to Williams, she's impressed with how Middleton was able to put makeup on and go out in public just hours after giving birth to Prince Louis. "No. And she was … standing!" Williams said laughing. "So she's officially No. 1."