Jermaine, who left the show on Monday night, claims that Ryan is acting up to the cameras.
Speaking on spin-off show Bit On The Side, Jermaine alleged: "I think [Ryan] has a game plan.
"He used to tell us ‘you’ll see how I am when we’re out’.”
He added (via the Daily Express): “When he thinks the camera is gonna be there he acts up and when it’s not he’ll have a snooze.”
Despite taking a swipe at Ryan, Jermaine insisted he had his back after the Roxanne Pallett 'punch' scandal.
After watching back the footage, he said: "Is that it? That’s poor, I was expecting something big. I feel like a mug because I comforted her.
“I was like 'I’m not gonna speak to Ryan'. That’s pathetic, what is she thinking?”
In last night's highlights, Ryan was left in tears after getting a letter from home.
His brother Scott wrote: "We are really proud. We know you're out of your comfort zone but trust me it's been well worth it.
"You've shown the nation just how amazing you really are and carried yourself so well. I know you'll be worried how you're coming across, but we want you to know that you've absolutely nothing to worry about. Everyone has seen the real you."
"Scarlett is missing her daddy," he continued. "So, so much and we've been showing her some clips from your challenges. She can't get her head around it - she smiles from ear to ear when she sees her daddy having so much fun.
"Lucy [Ryan's girlfriend] is more than proud of you and she's so happy everyone gets to see the Ryan she knows and loves."
Scott concluded: "Honestly just keep being you, you're doing us so proud."
Ryan reacted: "I love you so much bro"
Celebrity Big Brother 2018 continues nightly on Channel 5.