Washington (CNN) Former President George W. Bush and Michelle Obama are surprisingly close considering their political differences, and the 43rd president credits the former first lady's appreciation for his sense of humor as a key reason.

The unlikely pair have often been photographed together during formal events. When Obama embraced Bush at the opening ceremony for the Smithsonian National Museum of African American History and Culture last September, the photo of their warm interaction went viral.

"When I saw her, it was a genuine expression of affection," Bush told People magazine as he reflected on the moment. The interview was posted on Wednesday.

Former first lady Laura Bush, former President George W. Bush, first lady Michelle Obama and President Barack Obama attend the opening ceremony for the Smithsonian National Museum of African American History and Culture on September 24, 2016, in Washington.

The former President is back in the public eye to promote his new book, "Portraits of Courage," a volume of his paintings of military veterans.

The Bushes and the Obamas join hands during the singing of "The Battle Hymn of the Republic" during an interfaith memorial service for the victims of the Dallas police shooting on July 12, 2016, in Dallas.

"She kind of likes my sense of humor. Anybody who likes my sense of humor, I immediately like," Bush said.

The pair are often seated next to each other during events, including the interfaith memorial service for the victims of the Dallas police shooting in July, last year's funeral for former first lady Nancy Reagan and the 2015 commemoration of the 50th anniversary of the historic civil rights march in Selma, Alabama.

Former President George W. Bush speaks with first lady Michelle Obama during an event marking the 50th anniversary of the Selma to Montgomery civil rights marches at the Edmund Pettus Bridge in Selma, Alabama, on March 7, 2015.

"I can't remember where else I've sat next to her, but I probably have a few wisecracks and she seemed to like it OK," Bush said. "I needle her a little bit and around her, I'm fairly lighthearted. (The Obamas) are around serious people all the time and we just took to each other."

President George W. Bush greets Sasha Obama at the inauguration of Barack Obama on January 20, 2009, in Washington.