Meghan Markle, Kate Middleton, Prince Harry and Prince William All Attend Queen's Commonwealth Day Event

The Royal Family was all together Monday at a high-profile royal outing to celebrate Commonwealth Day.

Meghan Markle and Prince Harry greeted and chatted with Kate Middleton and Prince William outside the annual church service at Westminster Abby — where Kate and Will wed in 2011.

Kate and Meghan exchanged a friendly kiss on the cheek while the brothers shook hands, Meghan wearing a cream coat and cream print dress with Kate wearing a red Catherine Walker coat dress. They all chatted together as Charles and Camilla arrived.

Meghan was spotted giving a curtsy as the Queen, who wore a purple coat dress, arrived.

Commonwealth Day honors the family of 53 nations in the United Kingdom, some of which have the Queen as their head of state. The church service was targeted towards young people, as 60 percent of the population of the Commonwealth is under 30 years old. Grammy-winning group Clean Bandit performed, as did the U.K.'s biggest-selling tenor, Alfie Boe. Endurance swimmer, ocean advocate and UN Patron of the Oceans Lewis Pugh gave a reflection.

This year marks the 70th anniversary of the modern Commonwealth, which encompasses almost 2.4 billion people — a third of the world population. Last year, Harry was named as the Youth Ambassador for the organization by the Queen, which means that he and Meghan are making the Commonwealth a central part of their public life.

The couple have reportedly "beefed up security" in response to the racist hate messages the family has seen since they wed last May.

"The Royal Family is forced to be monitoring their social media feeds 24/7 because of all of the racist hate that Meghan has been receiving," a palace insider told Radar Online Thursday. "It has become a great problem."

The source claims the family is "on edge right now" so the Duke and Duchess of Sussex "beefed up security on them specifically."

Meghan and Harry are expecting their first child in late April or early May. They have chosen not to reveal the baby's sex, although one report suggests they do know if it's a boy or girl.

A source told Us Weekly that Meghan told guests at her Feb. 20 baby shower in New York City that she's having a boy, though a video of the pastel pink decorations at the event initially led royal fans to think otherwise.

Kate will also reportedly be throwing a baby shower for her as well in the U.K.

"There is still going to be some sort of private baby-centric event for Meghan's U.K. people, and Kate will host," a source told Us Weekly following Markle's star-studded NYC shower. "Her glam people and other relatives will be there. Not sure if it's a total baby 'shower,' but you could probably call it that."