NEW YORK, June 25 (Reuters) - The proposed combination of Kohlberg Kravis Roberts & Co and its Amsterdam-listed fund would have estimated earnings of about $425 million in 2010, an analyst at Sandler O'Neill calculated in a research note on Thursday.

On that basis, Sandler O'Neill estimates the combined entity will have a price-earnings multiple of 9.2.

Rival Blackstone Group (BX.N: Quote, Profile, Research) commands a multiple of 13 times earnings while Fortress Investment Group (FIG.N: Quote, Profile, Research) is currently trading at about 8.5 times, Sandler O'Neill said.

Private equity firm Kohlberg Kravis Roberts & Co announced plans on Wednesday to merge into its Amsterdam-listed fund, KKR Private Equity Investors LP (KKR.AS: Quote, Profile, Research) (KPE). However, no valuation was put on the proposed deal by KKR.

Analyst Michael Kim calculates an implied market for the combined entity of $3.9 billion, which he bases on KPE's closing price of $5.70 on Wednesday.

"As such, we think KPE is about fairly valued at current levels," said analyst Michael Kim in the research note. He raised his target on the stock to $6 from $3.50, roughly 10 times his 2010 proforma earnings estimate per share of 62 cents.

Sandler O'Neill calculated the earnings under a measure called "economic net income" which is how rival Blackstone reports.

Price-earnings multiples give investors a measure of how expensive a stock is relative to its earnings power. (Reporting by Megan Davies; editing by Matthew Lewis)