Carey and Cannon were together from 2008 until 2014, and are parents to four-year-old twins Moroccan and Monroe, and the report suggests the former couple has not yet settled financial issues in their divorce proceedings.
Packer's divorce from Erica, whom he split from in 2013, is also reportedly yet to be finalised.
Erica, who has three young children with Packer, is now dating Brit singer Seal, and the pair is reportedly expecting their first child together.
Following the engagement news, Cannon congratulated the happy couple in a funny post on Instagram writing, "#AllLove Congrats to @MariahCarey and James! May God Bless Your Future Union... #GreatPeople #GreatCouple".
- WENN