As Chris Brown celebrates his 25th birthday behind bars, his model girlfriend Karrueche Tran celebrates in his honor. She posted a cute birthday tribute to her Instagram account amid rumors he might propose!

One picture captures Tran sitting on Brown's lap in a backyard sporting birthday hats.

"Happy Birthday Christopher," she writes. "I love and miss you..can't wait to give you a big kiss and hug."

A source revealed to Hollywood Life that Brown plans on proposing when he gets out of jail.

"I don't know if that's him being lonely in jail but that's what he tells her," they told the site exclusively. "He calls her his wifey and tells her all the time that she's perfect wife material. He knows Kae is incredibly loyal and has literally put her life on hold to hold him down in jail. She's taken care of just about everything in his house."

They added, "He basically told her that when he gets out things are going to be way different between them and that he's going to return all the favors she's given him with a surprise of a lifetime."

As far as what Tran wants, the source thinks she would accept should the "Run It" singer pop the question.

 "Karrueche isn't sure. She's doesn't know but she was very happy when he called her 'wifey.' She loves Chris to hell and back - if he did propose to her, she would say yes."

According to The Daily Mail, the model has been hanging with pal Christina Milian to pass the time while Brown is away. They recently shared a photos together relaxing by the pool and taking a fitness class.

Tran stuck by Brown's side through a tumultuous love triangle with Rihanna, who he assaulted in 2009. He has had several run-ins with the law since the incident.

Would you be shocked if Brown proposed? Let us know your thoughts in the comments section below!