Marcus Grodd -- a two-timer?

The Bachelor in Paradise participant secretly dated another reality TV star while engaged to Lacy Faddoul, In Touch Weekly reported.

After Grodd fell in love with Faddoul in paradise and popped the question during the show's season finale, he reportedly starting dating Sydney Rae James, who stars on Eric & Jessie: Game On.

"They went on a date and kissed," a source told In Touch, adding that Grodd hid his engagement from James.

"Sydney thought his romance with Lacy was over."

Things got steamy on Grodd's date with James, according to the magazine.

"He was all over her," noted the source. "Meanwhile, poor Lacy has been planning their wedding this whole time. If she knew about Sydney, she'd flip."

Grodd, a 26-year-old in sports medicine from Dallas, TX, also appeared on Andi Dorfman's season of The Bachelorette during which he came across as an emotional, vulnerable, nice guy. However, he was forced to take a lie detector test during a group date and had lied about having slept with fewer than 20 women in his life.

Grodd insisted he was madly in love with Dorfman and completely devastated when she dumped him. However, he fell for Faddoul within moments of meeting the 26-year-old blonde -- who owns an elderly care facility in La Jolla, CA -- on Bachelor in Paradise.

Faddoul and Grodd have been dating now for a little over three months and have said they would like to get married in about a year.