2 sentences

1. 我只知道你的姓氏。

   wǒ zhǐ zhī​dao nǐ de xìng​shì.

   I only know your last name.

   Source: OpenSubtitles

2. 你的姓氏不重要。

   nǐ de xìng​shì bù zhòng​yào.

   Your last name doesn't matter.

   Source: AI Challenger 2017