我爸的儿子最帅我妈的女儿最萌
[wŏ bà de ér zi zuì shuài wŏ mā de nǚ ér zuì méng]
Translating this directly would give: 'My dad's son is the coolest, my mom's daughter is cutest'. It expresses a playful declaration of the superiority (in looks) and attractiveness of the user themselves and their siblings.