The news conference will take place at Mount Sinai Hospital where Ford is undergoing tests after a tumour was discovered in his abdomen last week, Coun. Doug Ford said as he entered the facility.
He announced he was running for mayor last Friday after his brother withdrew his bid due to his health. However, Rob Ford is running for councillor in the west Toronto ward he represented for a decade before he was elected mayor in 2010.
The mayor was hospitalized last Wednesday after complaining of unbearable abdominal pain and doctors discovered a "fair sized'' tumour. They did a biopsy, saying it would be about a week before they knew whether the tumour was cancerous.
Asked by reporters if his younger brother had received the test results, a grim-faced Doug Ford said a doctor would talk about it on Wednesday.
He was also tight-lipped about whether he would postpone his mayoral campaign. Earlier in the day, a spokesman said no campaign events had been planned yet.
"I just want to get over this hump on Wednesday, then we'll go from there," Doug Ford said.
Recent events have been "extremely tough" for the entire family, he said. The Ford patriarch, former Ontario politician and businessman Doug Ford Sr., died of colon cancer in 2006 just a few months after being diagnosed.
"Our family's strong, Rob's strong and with all the support of the people, that's what keeps us going," Ford said.
His brother and their family were grateful for the outpouring of support from the public and wanted to "reach out" to other people who are facing the same troubles, he said.
"It's not just about Rob Ford, it's the tens of thousands of families that are going through this, and so many families have met here," Ford said.
"It's heart-wrenching. But we just want to give our hearts and prayers to them as well. I appreciate everyone's support."
Ontario Premier Kathleen Wynne added her voice Tuesday, wishing Ford a speedy recovery.
"I hope Rob Ford can beat his health issues," she said at an event near Barrie, Ont. "I hope that he can be well and my thoughts are with him and his family."
But she didn't comment on his brother's decision to join the mayoral race. The provincial Liberals have mostly stayed away from the controversies surrounding Ford, saying his conduct should be dealt with at city council.
Ford returned just a few months ago from a stint in rehab after a second video surfaced showing him allegedly smoking crack cocaine, an audio recording of him making lewd comments about a female mayoral candidate and witness accounts of him snorting cocaine at a city nightclub.
It was another stunning chapter in a scandal-plagued year in which Ford was forced to admit to using crack cocaine in a "drunken stupor," became the target of a police investigation and was stripped of almost all of his mayoral powers by city council.
His tribulations garnered headlines around the world, with Ford becoming the butt of jokes on late-night television shows.
Wynne gently scolded reporters who asked who she intends to vote for as mayor of Toronto, where she lives.
"I'm not going to tell you that," she said with a chuckle. "We have a secret ballot."
She also declined to comment about Liberal MPPs endorsing former Progressive Conservative leader John Tory, the leading candidate for Rob Ford's job.
Interim Tory Leader Jim Wilson said the Liberals are clearly getting behind Tory, saying if he were one of the other candidates he'd be miffed.
Wynne said the province will need to work with the municipal leaders who will be elected this fall in 444 communities across the province, so she's remaining neutral in the elections.
NDP Leader Andrea Horwath says she stays out of the "endorsement game," but hopes what she calls progressive candidates are elected across Ontario.
— with files from Allison Jones in Ivy, Ont.