Denis Rooney effectively represents two acquisitions, as one part of it is a partnership and the other a limited company.
John Purvis, WYG's chief executive, said: "The acquisitions of Denis Rooney Associates and Denis Rooney Associates Limited represent the 18th and 19th acquisitions by WYG in the past five years."
He added: "These businesses are excellent acquisitions for WYG and should yield revenue growth, cost savings, incremental shareholder value and increased market presence."
Denis Rooney, the head of the merged firm, has been appointed chief executive of WYG Ireland.
The £4.3m was paid by £1.3m in cash, with the remainder made up by nearly £1.8m in shares.