So cute!! Reminds me of my cat's littermate - they had separate fathers so they look totally different but same mom, same litter.
The crying is normal, like everyone has said. Even when I had a kitten in a house with other cats, the kitten would cry... they get scared, its their first few days "alone" in the real world when they've been surrounded by their littermates every day previously. It'll take a little getting used to for the kitten, but they'll calm down soon. Just give it a little time!
Something to keep in mind, having two cats over one won't be much difference in the level of responsibility... a little more food, extra vet bills, but the cats will keep each other company. Also if your family was considering getting an additional cat in a few years, keep in mind that it is often easier to just start off with two kittens, the introduction process of a new cat can be rather lengthy. But, at the same time, your kitten won't have any issues being an only child either.