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Cassie Randolph Getting Serious with New Boyfriend ... Still Mum on Colton

Cassie Randolph still hasn't said anything about her ex, Colton Underwood, coming out as gay, but she's clearly moved on.

Sources close to the former 'Bachelor' winner and her new boyfriend -- 23-year-old singer-songwriter Brighton Reinhardt -- tell TMZ ... the 2 have been dating for a few months.

Though they've been spotted out together from time to time, their most recent outing is telling -- Brighton was hanging out with Cassie's family and we're told things are gettin' serious.

Cassie and Brighton spent the afternoon at the Shorebreak Hotel in Huntington Beach with her parents, along with her brother Landon, sister Michelle and her pretty famous boyfriend, Gregg Sulkin. Pretty good-lookin' crew.

As you may know ... Colton and Cassie dated after he gave her the final rose on his season as 'Bachelor,' but things fell apart and led to Cassie taking out a restraining order against him, which she later dropped.

We're told after she dropped it, there may have still been some bad blood, because Brighton dropped a song called "Creep" with the following lyrics --

"You can’t stop thinking about my baby / What once was yours in the world is changing / God, I hope you get your thinking right / GPS on the underside / Told her everything will be just fine / Damn, I can’t believe these guys." In other words, a clear shot at Colton.

Anyway, Colton recently revealed he's gay, and Cassie has yet to address it other than to say she wouldn't be discussing it, adding ... "There's a lot of layers to it, and I just think the best thing for me at this time is to move forward and just focus on going forward."

So the question ... why are both of them totally mum about each other? If we know anything here at TMZ, when people drop legal cases, they often agree not to trash each other or even mention the other person's name.

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