It seems Chris Brown is doing -- and saying -- everything he can to shore up his relationship with Karrueche Tran, now that the two are back together after a split. And apparently throwing his ex, Rihanna, under the bus is part of Brown's plan.

Maybe Rihanna meant something to Brown at one time, maybe she didn't. But the "Loyal" singer has been proclaiming to Tran that she means "everything" to him and that Rihanna is "nothing" compared to her, a source tells HollywoodLife.com in an exclusive interview.

After reuniting recently, "Chris told Karrueche, 'Bae, I'm about to man up. You've stole my heart and no woman has ever treated me the way you have. No one, not even any of my exes compare to you. You're my queen,'" the source told Hollywood Life.

Brown also apologized to Tran, specifically for comparing her to Rihanna and lying about her and Drake dating. He was like, "I don't know what I was thinking by saying that s***. Rihanna is nothing compared to you. You see I'm with you. I will never, ever compare you to her as long as I live. She doesn't even exist to me. You are my everything. Everything I am and have is because of you," the source told HollywoodLife.com.