Fiduciary Trust Co., a New York-based company that invests $29 billion for rich people and institutions, has agreed to buy $4 billion-asset Pennsylvania Trust Co. of Radnor, as it seeks more clients among rich baby boomers and their heirs.

Fiduciary Trust is owned by publicly traded Franklin Resources Corp., one of the national investment companies that has sought to diversify as the mutual fund industry, its best-known business, slows. The acquired wealth management firm will be renamed Fiduciary Trust Co. International, the buyer’s chief executive, John Dowd, said in an interview.

Though Franklin is based in California, the company’s Franklin/Templeton mutual funds are named for people with Philadelphia ties: U.S. founding father Ben Franklin; and the late John Templeton, the value-stock mutual-fund pioneer. Templeton left his fortune to endow the $3 billion-asset Templeton Foundation, of West Conshohocken, which grants the yearly Templeton Prize for “affirming life’s spiritual dimension.”

As part of the deal, Pennsylvania Trust chief executive George McFarland and his firm’s 60 employees will join Fiduciary Trust, Dowd added. He wouldn’t say how much his company agreed to pay. (The owner of a rival firm estimates the price topped $120 million, given Pa. Trust’s size, likely profitability, and the recent 8X pretax earnings that recent deals have topped.)

The smaller company’s board, which represents founder Richardson T. Merriman and the rest of the company’s 40 shareholders, approved the deal unanimously, said Pennsylvania Trust chief executive George McFarland. “We found the right partner at the right time,” McFarland added.

“Scale is really important in this business, and the way clients experience technology, outside their financial business, is changing their expectations,” pushing smaller firms such as Pennsylvania Trust toward larger, national partners that can fund staff growth and technology updates, Dowd said. He noted that his company also recently agreed to buy Boston-based Athena Capital, which manages $6 billion.

Fiduciary Trust has clients and a Delaware subsidiary but no office in the Philadelphia-Main Line area, so Pennsylvania Trust helps complete its national network, Dowd said. The average Athena client has $100 million invested; the average Fiduciary client, about $17 million; the average at Pennsylvania Trust, $3 million. Dowd sees room to grow.

Backed by Jonathan Butcher, who at the time was a boss of his family’s Philadelphia-based Butcher & Singer brokerage (now part of Wells Fargo Securities), Pennsylvania Trust was headed from its 1986 founding by Merriman, who had previously managed Pew (Sunoco) family money for Glenmede Trust Co. and served in the trust division at Girard Bank.

The Butchers sold Pennsylvania Trust to Penn Mutual Life Insurance Co., which sold it to Merriman and other insiders in 2011. The owners more than doubled its assets as it brought on additional money managers and their clients in the next nine years, while U.S. securities markets rallied.

Merriman “was quite a good investment adviser, with some good friends” in the brokerage and energy businesses, recalled Howard Trauger, who worked with Merriman at Girard in the 1970s, and later built and sold his own investment business, Schuylkill Capital, now part of Carnegie Investment Counsel of Cleveland.

Trauger said firms such as Fiduciary are naturally on the lookout for smaller firms with good local contacts: “Tremendous amounts of money are going to be transferred between generations. Those who understand that make sure they get invited to all the grandfathers’ wakes and granddaughters’ weddings, so they can be the guy managing the family funds. It’s a very cozy business.”

The deal makes sense for an old-line mutual-fund company such as Franklin Resources, says Robert Costello, owner of Costello Asset Management, Huntington Valley. “The mutual fund businesses are losing assets to Vanguard, which has lower fees. The trust companies are still doing well because all these baby boomers have to set up trusts for the next generation. There’s a lot of growth, and there’s not as much price competition in trusts," he said.

Indeed, Schwab and some other national discount brokerages aren’t included among the approved fiduciaries at Philadelphia Orphans Court, which directs wealthy people and their lawyers, who invest inheritances granted in wills that go through the city court, to hire from a list that includes local firms such as Pennsylvania Trust.