Young couples would do well to weigh the pros and cons of having children - as opposed to getting a dog or two. Let's take a lighthearted look at the objective and subjective aspects. The objective items, how long it takes, are not WAGs; I researched each one. Your results may differ.
Be aware: I've not sired any kids, so I may be prejudiced.
Objective. How long it takes to
Toilet/house train: Kids: 18-30 months Dogs: 4-6 months
Be able to feed themselves: Kids: 8-12 months Dogs: 8 weeks
Follow simple instructions: Kids: 10-24 months Dogs: 2-6 months
Safely leave alone in the house for 6 hours: Kids: 13-15 years Dogs: 1 year
Get them fully trained: Kids: 18 years? Dogs: 1 year
Winner: dogs. However, given their short lifespans, you have to start over every 12-15 years.
Subjective.
1. Responsible owners have their dogs spayed or neutered. Spaying and neutering one's kids is virtually unheard of - although a few parents wish they had. More importantly, it would deny the grandparents the opportunity to spoil them while in their care - and chortle when their parents retrieve them. Advantage: kids.
2. Dogs are excited when their owners return home. Kids, maybe. If they're hungry. Advantage: dogs.
3. Dogs alert you to strange noises and defend their turf. Kids, hardly ever. Advantage: dogs.
4. Dogs are warm and fuzzy and cuddly. Kids also, in their early years. But those teenage years, OMG! Most kids grow up to become helpful, enjoyable adults. Advantage: kids.
5. Once potty trained, kids take care of their own business. I've never heard of a dog that could use the WC and flush afterwards - or use a baggie to pick up the business. Advantage: kids.
Winner: kids.