The Canada Revenue Agency will be issuing the long-promised 'grocery rebate' payments to eligible Canadians on July 5. The food-inflation focused affordability measure is set to roll out to approximately 11 million low- and modest-income Canadians. Here's how much money those eligible can expect to receive.
I’m not sure, but I can think of two reasons for this:
Being a single parent is more expensive than being a couple. Because you can’t share costs with another person, a greater proportion of your income goes to required expenses like food, housing, and utilities.
Along those lines, food is cheaper per person the more people you buy for. Buying in bulk is a huge savings. This is presumably why they give you more money for the first child than for each subsequent child.