The pair are due to be unveiled as partners at a launch party in London next week, Financial News has reported.
Mobius left Franklin Templeton in January to launch his own asset management boutique.
Less than a month later, Hardenberg also resigned from the US-based asset manager, quitting his position as lead manager on the Temit fund, throwing carefully planned succession into disarray.
In February, Mobius revealed he is applying for fund management licences in London and Luxembourg to launch an open-ended, long-only emerging and frontier markets fund.
The fund is set to take an environment, social and governance approach to investing.
The announcement of Hardenberg’s exit from Franklin Templeton came one day after Mobius’s retirement from the firm.
Chetan Sehgal, based in Singapore, has been appointed lead manager on Temit, but has said he views Mobius as a mentor rather than a competitor as he moves to set up his rival fund.
In March, Mobius announced on LinkedIn that his eponymous firm was seeking to recruit investment analysts and a sales and marketing manager in its London office.
Seghal has worked in the emerging markets team for 22 years.
Franklin Templeton also brought in Manraj Sekhon from Fullerton Fund Management to serve in the newly-created role of CIO of Emerging Markets Equity in February this year.
Winterflood Investment Trusts cut Temit from its recommended list following Hardenberg’s departure, while Stifel touted the JP Morgan Emerging Markets investment trust as an alternative in an analyst note published this month.
Commenting on the news, Franklin Templeton said: “We wish Mark Mobius and his team well in their future endeavours. As announced in January, Manraj Sekhon was named CIO of Franklin Templeton Emerging Markets Equity, and he is focused on leading our team of over 70 experienced emerging markets investment professionals located in offices around the globe.”