"Cleared..Not Guilty! Finally my brother @oritsemusic three years of hell is over! No-one will ever know or imagine what he's been through," he wrote on Instagram alongside a picture of the star.
It continued: "I'm just so proud of the way he conducted himself during what has been the most awful time… he is so strong and I know he can't wait to start his life again now. We love you O."
Marvin's wife, Rochelle, who is also close friends with the singer, shared a touching post after the news broke. "This here is our brother, one of the kindest, most gentle, thoughtful men I know," she captioned a picture of the two of them together.
"Today he was cleared NOT guilty after 3 years of absolute hell. I'm so proud of how you have conducted yourself throughout this time, I really don't think I could have held myself in the same way. Reesh we love you so much and I'm writing this crying so many happy tears, it's over."
Oritsé, 32, has always denied the attack which reportedly took place after a concert in Wolverhampton in December 2016.
The singer's tour manager Jamien Nagadhana, 32, was also found not guilty of sexual assault and assault by penetration. The jury, of eight women and four men, deliberated for around two hours before unanimously acquitting Oritsé.