Bill Gross and his family own more than half of the bond fund he runs on behalf of Janus Capital Group Inc., after acquiring their shares through brokerage accounts at Morgan Stanley and Charles Schwab Corp.

Gross and his family held a 51.2 percent stake in Janus Global Unconstrained Bond Fund as of Dec. 31, according to a filing Friday by Denver-based Janus with the U.S. Securities and Exchange Commission. The shares had a market value of $739 million, based on net assets of $1.45 billion at year-end.

Gross began running Janus Global Unconstrained on Oct. 6 after his surprise departure from Pacific Investment Management Co., the Newport Beach, California-based company he co-founded in 1971. The fund’s assets soared from $13 million after Gross took over, and Janus Chief Executive Officer Dick Weil disclosed on a Jan. 22 conference call that more than $700 million came from Gross himself.

“William H. Gross, portfolio manager of the fund, is deemed to control the fund by virtue of owning more than 25 percent of the outstanding shares,” Janus said in today’s filing.

Gross’s investments helped fuel $2.8 billion of deposits into Janus’s bond funds in the fourth quarter and break a streak of 21 straight quarters of investor withdrawals. Janus is counting on Gross to restore growth at the firm, which at its peak in 2000 had assets of about $334 billion and now manages $183.1 billion, as of Dec. 31.

Gross, 70, is a billionaire who built one of the industry’s best long-term records while running the $134.6 billion Pimco Total Return Fund and helped expand Pimco to oversee about $2 trillion at its peak. He left Pimco on Sept. 26 after clashing with senior executives.

According to Janus’s filing, New York-based Morgan Stanley held 62.5 percent of the Janus Global Unconstrained’s institutional shares on behalf of customers as of Dec. 31. San Francisco-based Charles Schwab held 9.91 percent of the institutional shares on behalf of clients.

With respect to the institutional shares the two brokerages hold for customers, 62.1 percent represents investments “held beneficially by William H. Gross including his family,” according to the filing. “Mr. Gross (including his family) owns 51.2 percent” of the fund when all share classes are included.