After a personal pronoun (你, 我, 他/她, etc.), 的 is frequently omitted, especially in casual speech, when what follows is a family member. This rule can also apply to nouns such as
家 ( jiā ) and 男朋友 (nán péng yǒu )/女朋友 (nǚ péng yǒu).
我家有三个卧室；我爸妈的卧室最大，我弟弟的最小。
wǒ jiā yǒu sān gè wò shì ；wǒ bà mā de wò shì zuì dà ，wǒ dì dì de zuì xiǎo 。
My house has three bedrooms; my parents’ room is the biggest; my younger brother’s is the smallest.
我女朋友的哥哥是我妹妹的男朋友。
wǒ nǚ péng yǒu de gē gē shì wǒ mèi mèi de nán péng yǒu 。
My girlfriend’s older brother is my younger sister’s boyfriend.
[1] Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.
