Jack Osbourne Marks 18 Years Sober with Message of Hope for Others Struggling with Addiction

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Jack Osbourne is 18 years sober — and he's letting others know that it's possible to get to where he is today.

Ozzy and Sharon Osbourne's son marked the milestone on his Instagram Thursday, sharing a screenshot from his 12-step program page showing that he's reached 18 years of sobriety.

"It's not that it get[s] easier or harder, It's just that it's life on life's terms," he wrote in the caption. "If anyone is trying to get sober, know that it [is] possible if you are willing to do the work. Sending lots of love to my people who have been on this journey with me. #sobersbetter"

Jack, 35, has frequently opened up about his addiction and his struggles to remain sober, especially through his multiple sclerosis diagnosis in 2012.

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RELATED: Jack Osbourne on Staying Sober After MS Diagnosis: I 'Focus on What's Right in Front of Me'

Last April, the star explained in an Instagram post for his 17-year anniversary that he got sober from drugs and alcohol when he "surrendered to the fact that I will never be a 'normal' drinker and that drugs and alcohol will only ever lead to bad things for me. I went to meetings, worked steps, help newcomers and surrounded myself with strong sober people."

Others in his famous family, including dad Ozzy and sister Kelly, have also been open about getting and staying sober. Earlier this week, Kelly, 36, revealed that she recently "relapsed" after four years of sobriety, but is now "back on track."

"This is a little hard for me to talk about, but I've always promised you that I will always be honest with you about where I'm at and what's going on in my road to recovery," she told fans on her Instagram Story Monday.

RELATED VIDEO: Kelly Osbourne Reveals She 'Relapsed' After Almost 4 Years of Sobriety: 'Not Proud of It'

"I relapsed. Not proud of it," she continued. "But I am back on track, and I will be doing a podcast this week where I tell everybody about what's going on and what happened."

The Project Runway Junior judge went on to say that she was "sober today and I'm gonna be sober tomorrow, but it truly is just one day at a time."

"And I just wanted to tell you guys the truth, 'cause I never, ever want to lie to you," Kelly said, concluding, "Thank you so much for your support and your love, and you'll be hearing from me soon."

If you or someone you know is struggling with addiction, please contact the SAMHSA substance abuse helpline at 1-800-662-HELP.