The couple last were seen together in May at the American Museum of Natural History gala in New York, Entertainment Tonight reported.
"They're kind of leading separate lives," said George Rush of the New York Daily News.
Others explained that Schlossberg travels frequently and doesn't care to go to the social and charity events Kennedy is obliged to attend.
Kennedy and Schlossberg have been married almost 20 years and have three children, 17-year-old Rose, 16-year-old Tatiana and 13-year-old John.
Were they to separate, Kennedy's multimillion-dollar fortune, which has increased considerably since the deaths of her brother John Jr. and mother Jackie, could be split unless a pre-nuptial agreement were signed. Experts say it is unlikely she married without such a contract, Entertainment Tonight reported.
Some say the rumors are unfounded and the marriage is solid.