Kim Williams, chairman of the Thomson Reuters Founders Share Company, was not available for immediate comment.
Reuters was unable to determine who would lead the new division.
"Thomson Reuters has been in mergers and acquisitions mode for some years now, but this will mark a step change", said Alex DeGroote, an analyst at Cenkos Securities in London.
Thomson Reuters now trades in NY and Toronto with a market value of around $31bn.
The company also said it would retain full ownership of its legal, tax and accounting and Reuters News businesses.
The sources cautioned that a deal had not been finalised and could still fall apart.
It is unclear how the proposed deal would be viewed by trustees of the Thomson Reuters Founders Share Co, which was set up to oversee Reuters' editorial independence when the company was first publicly listed in the 1980s.
Thomson Reuters expects the transaction to close in the second half of 2018.
According to reports from Reuters, Blackstone is seeking a 55% stake in the business, which has been in the doldrums since the 2008 crash but is now viewed as an undervalued asset in a market characterised by robust growth and a slew of new data-hungry regulatory measures.
Blackstone, which already has business relationships with most of the major banks on Wall Street, bought a small financial information business, Ipreo, in 2014. The news and data provider has a market value of about $31 billion and its shares trade on the NY and Toronto stock exchanges.
The financial and risk business faces challenges from cost-cutting among clients, including over a trend towards passive investing, weak investment-banking results and the introduction of MiFID II, analysts at Berenberg wrote in a January 18 note. But amid tougher regulations around risk-taking, the regulation and compliance business has been a bright spot.
"As a long-term value investor, we believe this business transformation will enable F&R to focus on its core customer base and be in a strong position to continue delivering innovative products to the market", said Choo Yong Cheen, chief investment officer of private equity at GIC.
In 2016, Thomson Reuters sold its science and intellectual property division for $3.55 billion (U.S.) in cash to Onex Corp. and Baring Private Equity Asia.