Yes. An indefinite noun phrase usually becomes definite after it has been mentioned once. The second time it is mentioned, it is definite.
我认识一个姓白的中国人，他是我的中文老师。 (他 is definite.)
wǒ rèn shí yī gè xìng bái de zhōng guó rén，tā shì wǒ de zhōng wén lǎo shī。
I know a Chinese person whose last name is Bai; he is my Chinese (language) teacher.
[1] Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.
