Former Liverpool chairman Broughton's consortium includes World Athletics President Sebastian Coe and wealthy investors from around the world, who the group says all want to maintain Chelsea's top status.
Private equity veterans Josh Harris and David Blitzer, who own sports teams including the National Basketball Association's Philadelphia 76ers, are also backing Broughton's bid.
Williams and Hamilton have pledged an estimated 10 million pounds ($13.06 million) each to the bid, the reports indicated.
Hamilton's representatives later confirmed that the 37-year-old had joined Broughton's bid, but said the financial figures quoted in the report were not accurate, without disclosing any details.
Williams is already an investor in Los Angeles' Angel City FC, which plays in the National Women's Soccer League.
Final bids for the club, which was put up for sale by owner Roman Abramovich following Russia's invasion of Ukraine before sanctions were imposed on the oligarch by the British government, were submitted earlier this month.
Others on the shortlist to buy the English premiership club are LA Dodgers part-owner Todd Boehly and Boston Celtics co-owner Steve Pagliuca.
A consortium led by Chicago Cubs owners the Ricketts family pulled out of the running.
The club's sale is being overseen by US bank Raine Group.