Casper Smart on Wednesday took to Twitter to wish his girlfriend, singer Jennifer Lopez, a happy 44th birthday in a personal message addressed to his "bear."

"HAPPY BIRTHDAY to my very very beautiful bear the nicest, sweetest, funniest, sexiest bear there is!" he wrote. "Love u."

Smart, 26, and Lopez have been dating since 2011 following the singer's split with her third ex-husband, Marc Anthony. The couple have since adopted a brown boxer puppy together whom they named "Bear." When Smart tweeted on Jan. 17, about the "new addition to the family," Lopez re-tweeted the message with a note that it "could get confusing," since she and Smart use "bear" as their pet name for each other.

The Live It Up singer celebrated her birthday at her new Water Mill estate in The Hamptons, N.Y. with Smart and several friends including Alicia Keys and record executive L.A. Reid, according to The Nation. The bash, held on the estate of Lopez's $10 million mansion, featured a trampoline and an array of party games such as water balloon fights. There was also a sack race and a source reportedly told New York Post that the "clear winner" was Smart. 

"Her birthday was so much fun and she's still celebrating," a source told Us Weekly. "Casper is fantastic and they are in a good groove right now and the kids are adorable. All is well but things have just been busy!" 

Lopez talked to Harper's Bazaar earlier in 2013 about her dating life, saying she could not be more thrilled with how things are playing out..

"He's fantastic; he's like my best friend. I can tell him everything, when I'm feeling down, when I'm feeling good," she told the magazine in January about Smart. "He gives moral support, endless love and support."

Lopez has 5-year-old twins Max and Emme with Anthony. 

Tags: Jennifer Lopez Casper Smart