The 19-year-old divulged the news in a trailer for the upcoming reality show The Houstons: On Our Own, which stars Brown and the extended family members of the late Whitney Houston.
© WENN / Apega/WENN.com
© WENN / ABC
Houston informally adopted Gordon, now 22, when he was 12.
Rumours of a romance between Brown and Gordon emerged in the spring, shortly after Houston's death in February.
Representatives for Brown initially denied the reports, but in a new promotional video, the teen admits to the relationship.
A clip from the preview features Brown tentatively revealing the engagement to shocked family members, prompting the response: "No-one knew that from a godson, you would turn into a boyfriend, nobody knew that."
"They wanna see us fail," Brown says at the end of the preview. "I've got one thing to say - 'You won't!'"
The Houstons: On Our Own will premiere on the Lifetime network on October 24.
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