Brown, 27, who recently gifted Santiago a diamond watch on her 25th birthday, wants to prove her that he is serious about their relationship, reported Hollywood Life.
"Chris and Krista are dating. But he's learned from his relationships with Rihanna and Karrueche Tran, and is going to keep this relationship out of the media and on the lowest of the down lows," a source said.
"But just because they're keeping it quiet doesn't mean it's not passionate. They're into one another heavy. He's showered her with gifts. The most serious gift he's given her is the key to his house. That's huge for him because he wants her to know that he's serious about her," the source added.