5 sentences

1. 他是徒先生的长子。

   tā shì Tú xiān​sheng de zhǎng​zǐ.

   He is the eldest son of Mr. Tu.

   Source: Dong Chinese Dictionary

2. 他是家里的长子。

   tā shì jiā lǐ de zhǎng​zǐ.

   He is the eldest son in the family.

   Source: Dong Chinese Dictionary

3. 在兄弟排行中，伯代表的是家里的长子。

   zài xiōng​dì pái​háng zhōng, bó dài​biǎo de shì jiā​lǐ de zhǎng​zǐ.

   In the order of seniority among brothers, 'Bo' represents the eldest son of the family.

   Source: Dong Chinese Dictionary

4. 按照家乡的习俗，长子必须在灵堂前为父亲守灵。

   àn​zhào jiā​xiāng de xí​sú, zhǎng​zǐ bì​xū zài líng​táng qián wèi fù​qīn shǒu​líng.

   According to the customs of his hometown, the eldest son must keep a vigil for his father in the mourning hall.

   Source: Dong Chinese Dictionary

5. 我听爷爷说，他年轻的时候曾在山西的长子生活过。

   wǒ tīng yé​ye shuō, tā nián​qīng de shí​hou céng zài Shān​xī de Zhǎng​zǐ shēng​huó guo.

   I heard from my grandfather that he lived in Zhangzi, Shanxi, when he was young.

   Source: Dong Chinese Dictionary