And their presence hardly went unnoticed.
A Wimbledon selfie-snapper accused of invading the Duchess of Sussex's privacy told The Sun: "I had no idea she was there!" "It was an honor to play in front of her".
Later on, Kensington Palace shared a video on its official Instagram account of Simona Halep dropping a very low curtsy to the Duchess of Cambridge when they met off court while Kate offered effusive congratulations to the new champion.
However, her outing turned out to be a controversial one. Last week, Meghan Markle had made a surprise trip to the courts, where 23-time grand slam victor Serena was playing against Kaja Juvan.
"While parents will adopt their own styles of holding and comforting their babies in a range of ways, the way Meghan is pictured holding Archie is actually a commonly recommended hold", she said.
"Just having her in general as a friend is great".
When Markle attended Wimbledon last week, she sat in between two of her female friends. "Always positive no matter what", Williams said.
Meanwhile, other than the criticisms that Markle received from shunning away royal fans at Wimbledon, she was also criticized when she took her son, Archie, to Prince Harry's polo match.
TV cameras captured that meeting minutes later, with Halep giving a deep curtsy as she was introduced to Kate before heading out to the balcony to show off her trophy to fans outside. "It was really, really impressive, so congratulations".
Snigur trailed 4-1 in the opening set before winning five straight games, then came from 3-0 down in the second set.
He said: "I honestly couldn't really care less about taking a picture of Meghan, Harry or any of the royals - and, if I did, I'd ask first".