Private equity-backed Pathstone and Cornerstone come together in the latest RIA mega deal. : Pathstone, a private equity-backed family office in Englewood, N.J., announced its acquisition of Cornerstone Advisors, a registered investment advisor headquartered in Bellevue, Wash. The transaction would create an RIA with $20 billion in assets under advisement. The acquisition, advised by Raymond James’ investment banking team, grows Pathstone’s capabilities and offerings. The combined firm will have 200 employees across nine offices. Cornerstone will bring over 65 employees and 22 new partners.