06/23/2010 at 08:00 PM EDT
Jeremy London's family can no longer remain silent.
They've watched with increasing concern and frustration as the bizarre police case in Palm Springs, Calif., has unfolded – with claims the Party of Five
star was allegedly kidnapped
and forced to take drugs.
They think there may be another explanation.
"We love Jeremy, we only have his best interests at heart," his twin brother Jason London, 37, also an actor, tells PEOPLE. "We feel he needs serious psychological help and drug treatment as soon as possible."
After reaching stardom on the hit show, Jeremy has endured a series of struggles that he has not denied. He recently told PEOPLE about his fight to stay sober
, his bitter custody battle with his ex-wife Melissa over son, Lyric, 3, and his widespread financial troubles.
Now his family fears he's hit another low point.
"Jeremy's behavior right now is indicative of whenever he's back on drugs," brother Jason says. "The fact that he's lashing out against his own family and has shut us out is just one more sign of how sick he really is."
Jeremy insists his story is true – and police so far believe him, arresting a 26-year-old man on kidnapping and other charges. In a video statement
to RadarOnline, Jeremy vented his anger at his mother and brother for openly questioning the validity of his abduction and for spreading "outrageous lies" about him, and has legally threatened his family not to speak to the press.
His family reacts with sadness and frustration.
"It's absolutely false that we're telling lies about Jeremy," Jason says. "We would never do anything to hurt him. But Jeremy and Melissa's story of the kidnapping just doesn't add up. None of it makes any sense. Mainly, why didn't Melissa call the police if Jeremy went missing with these strange men until 2 a.m.?"
His brother adds: "For years we've been worried sick about getting a phone call telling us that Jeremy's been found dead. For months, Jeremy has cut off his whole family and he refuses to talk to us. We're desperate for anyone to get him help and that's why we're speaking out."