“Happy birthday dear Britney f—ing Spears,” Oliver sings in the clip.
On Friday, the pop star shared a video to Instagram that featured the siblings singing “Happy Birthday” to Britney in honor of her 40th birthday.
As shown in the clip — which appeared to have been shot by Kate — Oliver, 45, started singing the song, performing a smooth version of the track. The “Nashville” star’s 3-year-old niece — Kate’s daughter, Rani, — provided some adorable backup vocals.
“Happy birthday dear Britney f—ing Spears,” Oliver belted out. Kate, 42, then joined her brother and daughter to finish the song.
After showing shots of Rani and Oliver, Kate turned the camera on herself and blew a kiss.
“⚰️⚰️⚰️ @katehudson @theoliverhudson,” Britney captioned the video, above. Kate commented on the post with a heart emoji.
According to Page Six, the “Baby One More Time” singer is longtime friends with Kate and Oliver.
Britney turned 40 on Thursday, which marked her first birthday following the recent termination of her 13-year conservatorship.
The Grammy winner took to Instagram on her birthday, sharing a sweet video montage of footage from her vacation with fiancé Sam Asghari, including a photo of a balloon display that featured the words: “Happy Birthday Britney.”
“I’m so blessed and grateful !!!! Tears of joy today 🥲,” Britney wrote in the caption of the post, above.
Britney and Sam, 27, became engaged in September. Sam shared a sweet birthday tribute to Britney on Instagram, referring to her as his “wife” in the caption.
“I call you Lioness because I admire your relentless strength, I’m inspired by your beautiful heart, I celebrate your smile that lights up my world ❤️,” he captioned two photos of himself and Britney, below. “Everyday is your birthday my queen 👑 Happy 1st birthday to my wife 🥳 #dec2nd @britneyspears.”