The pair welcomed their twins into the world on Saturday and, following days of speculation, have finally confirmed the monikers of their daughter and son.
According to Mariah's spokesperson, Monroe – who is named after late actress Marilyn Monroe, one of the singer's biggest inspirations – does not have a middle name because her mother doesn't have one.
Her brother shares his middle name with his father, as well as it being his grandmother's maiden name.
The top tier of the 42-year-old singer's New York apartment is called the Moroccan Room – because of its African-inspired décor – and is the place where Nick proposed to her.
Mariah's spokesperson Cindi Berger said: “It has been a long, emotional journey for this family, and I couldn’t be happier for all of them.”
Earlier this week, the 'We Belong Together' hitmaker teased fans by revealing the twins' names both began with the letter M and invited her twitter followers to guess at what they have been called.
She tweeted: "I wish I could personally thank all those around the world who continue 2 send congrats+prayers for #dembabies! they're doing great (sic)."
"And they are the most incredible gifts we could ever have imagined (sic)!"
"So we r bout 2 reveal the actual names and b4 we tell em 2 our friends etc. both begin w/M's (sic)!!!!"