"I would be very surprised if he didn't meet them, as it was a national tragedy which touched many," said Vatican spokesman Federico Lombardi, though he said he could not confirm when or where during the five-day visit the meeting would take place.
The Sewol ferry sank in April with the loss of some 300 lives -- most of them schoolchildren -- and the tragedy rocked the entire country.
The pope will arrive in Soeul on August 14 and is scheduled to meet South Korean President Park Geun-Hye at the Blue House before travelling the following day to Daejeon for a mass with thousands of faithful at the Purple Arena football stadium.
The 77-year-old, a champion of the weak and downtrodden, will go on to visit a centre for the handicapped in the village of Kkottongnae -- "field of flowers" in Korean -- before winding up the trip with a mass for inter-Korean reconciliation and peace in Soeul's cathedral.
The two Koreas remain technically at war because the 1950-53 conflict ended in a ceasefire, not a peace treaty.
Some five million of South Korea's 50 million people are Catholic, alongside seven million Buddhists, around 15 million Protestants and numerous followers of new religious movements.