I'm damned if I know who he is.

我根本不认识他。

《牛津词典》

Although I don't know who he is, I know who he is for.

虽然我不知道他是谁，但我知道他是为了谁。

youdao

Or rather , I know who he is.

或者不如说，我知道他是谁。

youdao

This guy--I don't know who he is but he seems to be on a lot of these things but the thing is you don't need to rely on him.

这个家伙，我不知道他是谁,不过他看起来在很多这类地方出现,但你不必依赖他做的表情。

耶鲁公开课 - 心理学导论课程节选

I do know someone who is fully supported by the government because he was in the army,

我知道这样一个人。他的学费完全由政府来缴纳，因为之前他在美国军队服役，

拿全额奖学金 - SpeakingMax英语口语达人

This eBay auction is giving you a chance to own 1, 950 (3.75 inch) action figures, from your favorite characters (Han Solo in Carbonite Chamber) to the more obscure ones (Nien Nunb) (Actually, I know exactly who he is.) These figures have been documented in the recently released book, Star Wars: The Ultimate Action Figure Collection by Stephen Sansweet, which covers the 2, 500 figures that have been released in the last 35 years.

FORBES: Collection of 1,950 Star Wars Action Figures Up for Grabs on eBay

"I must admit, I don't know who he is, " says Herminio Batalla, as he enjoyed his paper on a park bench.

BBC: Mexico row over Azeri leader Heydar Aliyev's statue

Now, Sullivan is a blogger who I have the deepest admiration for, and like many other bloggers I know, he is one of the reasons I blog today.

FORBES: Getting Rid of Bad Teachers