The singer/actor was linked to Houston aft...
The National Enquirer claims the I Will Always Love You hitmaker, 47, has been "quietly dating" Gibson ever since - but the relationship is news to the hunky star.
In a post on Twitter.com, he writes, "Negative blogs, press, blurbs, people spreading negative things. Rumors. I rest WELL at night cause none of these things matter anymore...
"#NEVER... I repeat.. NEVER..!!"
But Gibson's harsh denial has irked Houston's daughter, Bobbi Kristina.
Responding to the actor's tweet, she writes, "Damn it's like tht (that)?! Hah, well to clear it up, TRUST ME, MY MOM WOULD NEVER. Hah #shesroyalty."