"Liam's entire family flew over for the holidays and the Cyrus family were in town too. It just seemed like a no-brainer to do it while everyone was together," they noted.
On the night, Miley posted a photo with the hash-tag "in laws", featuring Liam and Chris's mum, Leonie Hemsworth, with her mum, Tish Cyrus, and with Elsa Pataky's mum Cristina Pataky Medianu.
The couple reportedly wrote their own vows for the ceremony, confessing that they were each other's soulmates.
It's also reported the couple are hoping to start a family soon.
Daily Mail Australia has contacted the couple's representatives for comment.
Indeed, as the clock struck midnight the loved-up pair enjoyed a passionate kiss, which the popstar happily shared with fans on Instagram.
The intimate moment, caught on camera, was posted without any caption but the picture did all the talking, with over half a million likes in the first hour.
Earlier in the night the 24-year-old singer shared a photo of her handsome fiancé in a cheeky Instagram post.
The snap shows the 26-year-old standing in front of Miley, hand outstretched as though he is asking her for a dance.
Liam wore shiny gold trousers and a black shirt left slightly unbuttoned to expose his muscular chest.
Miley accompanied the photo with the caption: "Sorry. My dude is HOT."
The couple, who rekindled their engagement in late 2015, rang in the new year at a fancy dress party understood to be held at SeaWorld San Diego.
They were joined there by Miley's mum Tish Cyrus, as well as the Hemsworth and Pataky clans.
Chris and Luke Hemsworth were both there, as were the famous brothers' parents.
Elsa Pataky, wife to Chris, partied the night away along with her mother and sister.
In another cute snap, Miley posed for a selfie with her mother Tish Cyrus.
The Wrecking Ball star accessorised with rainbow stick-on diamontes and slicked back her hair with gold glitter.
In Elsa Pataky's Instagram photos, the Spanish actress posed next to her friends, including her sister-in-law Samantha Hemsworth and future sister-in-law, Miley.
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The singer accessorised in typical quirky style, and appeared to make a lewd gesture as she posed for the photo.
The soirée was held in the US, as Elsa and husband Chris Hemsworth are shooting a film together in New Mexico.
