With his marriage and career in crisis, family members fear CHELSEA CLINTON’s new husband MARC MEZVINSKY is cracking up, The ENQUIRER reports exclusively!

"Marc has us ALL worried. I think he’s clearly undergoing a crisis," Marc’s first cousin, Andrea Mezvinsky, told The ENQUIRER.

Six months after marrying into the world famed Clinton clan, 33-year-old Marc abruptly quit his cushy job with a Wall Street investment bank and headed to Wyoming to be a ski bum.

As media erupted, Marc returned for some quickie casual photo cops with the Chelsea on the streets of Manhattan.

Marc’s family is deeply concerned that the erratic behavior could be a sign of mental problems, said Andrea, a successful comedian who has appeared on The Oprah Winfrey Show.

"He’s known Chelsea for a long time, but I think he’s having trouble coping with the pressure of being in the spotlight."

For the full story with all the details and the truth about Marc’s estranged father — it’ s only in the new ENQUIRER!