In Touch has exclusively learned that after Marcus Grodd proposed to Lacy Faddoul on the season finale of Bachelor in Paradise, he secretly started dating another reality star, Sydney Rae James!

“They went on a date and kissed,” says an insider, adding that Marcus hid his engagement from the E! Network’s Eric & Jessie: Game On star. “Sydney thought his romance with Lacy was over,” says the source.

“He was all over her,” the insider tells the mag. “Meanwhile, poor Lacy has been planning their wedding this whole time. If she knew about Sydney, she’d flip.”

For more on this story, and for all the details behind Bachelor in Paradise and your favorite reality stars, pick up the new issue of In Touch Weekly, on stands now.