Reality Check    
According to a study by the US Department of Agriculture, a family with a child born in 2015 can expect to spend about $233,610 for food, shelter, and other necessities to raise that child over the next 17 years.
If costs were spread out evenly over that 17 year period, they would add $1,145 to your monthly expenses. Monthly costs for children will not be added to your Monthly Expenses at this point. You may have already accounted for some of that cost (i.e., size of house) and you will want to include a spouse's income when deciding on your family budget.