No, children are not needed. Not a requirement. Thank goodness!
However, children are eligible for sponsorship in most situations. There's several different ways it can play out - including stepchildren and adopted children - but none are necessary for spousal immigration.
The 2 year rule - Conditional PR.........
- Been married less than 2 years - you are a Conditional PR for 2 years after landing
- Been in a CL relationships less than 4 years - you are a Conditional PR 2 years after landing
- Been married more than 2 years, CL more than 2 years, or have a child together - no Conditional PR applies
Here is a guide - I found the guides very helpful.