美得像你大姨妈帅的像你大姨夫
[mĕi dé xiàng nĭ dà yí mā shuài de xiàng nĭ dà yí fū]
This is a playful and somewhat nonsensical nickname. It's using exaggerated terms referring to family members, implying that 'I am so handsome that it resembles an older male relative and my beauty rivals that of an aunt'. However, it’s more of a joke in context because these descriptions are unconventional for praise and thus create a funny effect.