How to say "oink!" in Mandarin in a family situation? This may not be on-topic for the next 4383 days, but hopefully today someone will help me out.

Last year was the year of the dog, and a common way to write (in English) the Chinese version of what dogs say is wang! wang!.

Today is the first day of the year of the pig. How would I write in English and say  what pigs say in Chinese? 

I'm looking for something that could be polite and humorous in a family situation and generally recognized in Mandarin, if such a thing exists.
Well, the porcine vocabulary comprises at least 3 sounds. How one may represent them is a matter of choice. To date, no exhaustive linguistic studies, to my knowledge, exist.
'oink' is phonetically interesting, because the sound is produced by inhaling. To mimic the 嗷嗷 grunt adequately, one should also inhale.

grunt: 嗷嗷，呼噜噜
squeal: 吱儿吱儿
oink(somewhere between grunt and squeal): 哼哼, 耶耶

当然，不同地方的猪叫声是不一样的， 因为各个地方的方言不一样。
东北的猪叫声听起来和广东的不一样。