The former glamour model admits Harvey, 18, has started to ask Carl, 31, to do things for him around the house and even tried to stop him going to work so they could hang out together.
Doting mum Katie told Daily Star: "Even through Harvey doesn't talk like us he is very clever.
"He draws pictures for Carl and he asks him to do things for him.
"He calls Carl his best friend."
After Carl chimed in: "He wanted me to stay with him all day the other day," Katie added: "Oh yeah, he didn't want him to go to work."
Daily Star previously revealed how Katie and Carl are trying to help Harvey lose weight by working out together.
Harvey suffers from Prader-Willi syndrome as well as being partly blind and autistic.
He is currently reported to be 29 stone due to his excessive appetite cased by the syndrome.
Katie said: "We have now got a gym as I had to get one for Harvey.
"So, fitness for us is the way forward... unless Carl gets me pregnant.
"When I say workout, anything is better than nothing with Harvey."
Katie splashed out on a new treadmill for training after her ex Kris Boyson took her old one, sparking a major row.
Kris insists it was broken and Katie told him he could have it, but Pricey claims this isn't the case.
Hitting back at Katie's claims, Kris told Daily Star: "Kate was throwing a treadmill away as it was broken, she gifted it to me and I spent money rewiring it and fixing it.
"Now it’s fixed she wants it back? I don’t believe she wants it back, I just think she’s using me for another story.
"First it was her mum that wanted it, now it’s Harvey, make your mind up.
"Surely by now Carl is getting the hump that Kate keeps mentioning my name."
Detailing the row earlier this summer, a source told Daily Star: "Katie is determined to get her gym equipment back so her mum Amy can use it to try and improve her health.
"During their relationship, Katie made Kris a home gym as she knew he was big on his fitness – one of the items was a treadmill.
"When they split, he took it with him and now won't give it back despite asking her a few times.
"He sees it as his, as he bought a new belt for it so doesn't see why he should have to return it."
The insider added: "The whole thing is trivial but over the past few weeks Katie and Kris' relationship has deteriorated.
"Katie has had enough of drama and simply wants to get back what she sees as her own.
"All she wants is closure and an apology."