The two, who starred in a Broadway show together, were spotted sharing a "passionate" kiss on May 9, according to the New York Post's Page Six.
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Jake and Ruth have been linked since December. In Las Vegas over fight weekend on May 2, the duo attended the same pre-fight party, as well, although they didn't arrive or leave together.
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Over the weekend, though, the two took a fitness class together in New York, where they were in full "workout mode." After a hard day in the gym (and after they freshened up following the boot camp-style class,) they shared a "passionate but tasteful kiss" before leaving separately, the report said.
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Recently, Jake told Ellen DeGeneres that he is, in fact, "single." Well, maybe not for much longer…