Jacob Sartorius has offered a special greeting for Millie Bobby Brown on her 14th birthday.

After exchanging sweet Valentine's Day posts, Sartorius and Brown returned to Twitter with more adorable messages for each other. The teen singer recently shared a black-and-white photo of him and Brown, declaring his love for the TV star in the caption.

"Happy birthday to this beautiful girl, 14," he posted. "you're the funniest, most caring person in the entire world. I hope this year brings you lots of great memories and moments you remember forever. Can't wait to see you, I love you and miss you so much!! Everybody go wish this girl a happy birthday @milliebobbybrown."

As previously reported by Us Weekly, the young couple's relationship started from a close friendship. They started spending more time together and fueled romance rumors earlier this year. The "Stranger Things" actress later confirmed the news by posting a photo of herself resting her head on the musician's shoulder via Instagram Story. She then captioned the image with three heart emojis.

In addition to their romantic social media posts, Sartorius and Brown spent the past New Year's Eve at Walt Disney World in Orlando, Florida with her family. Brown also shared a photo of them looking into each other's eyes on Feb. 14.

"They're really crazy about each other," an insider told Hollywood Life about the pair's romance. "But they're both still really young and have really busy work schedules, so they don't spend all their time in each other's pockets."

Earlier this month, Brown was spotted backstage at the 15-year-old crooner's concert on Jan. 31 in Atlanta, Georgia. Photos and videos obtained by TMZ show the 14-year-old actress hiding behind a curtain while smiling. Sartorius was performing on stage when the footage was taken.