New York-based Tiedemann Wealth Management (TWM) has agreed to buy Threshold Group, a Seattle-based wealth advisory firm and family office, for an undisclosed sum.

Threshold Group, established in 1998 by Jane and George Russell, manages around $3.4bn in assets. The firm has currently assigned $1.5bn for impact investments.

The combined entity will manage around $15bn in assets and will operate under the Tiedemann Wealth Management brand. The deal is expected to be completed in December 2017.

The Russell family will acquire certain amount of ownership in Tiedemann Wealth and Eric Russell will join Tiedemann Wealth board as part of the deal. Michael Tiedemann will become the CEO and chairman of the board of the combined entity.

“Many of our clients have shown interest in impact investing. The addition of Threshold’s expertise in this area to our existing investment platform and comprehensive services will be a welcome addition for our clients today and prospects in the future,” Tiedemann noted.