If you've ever read and enjoyed works like "Yotsuba&!", "Barakamon", "Usagi Drop" and "Azumanga Daioh", you'll probably love this series too!

The manga follows two brothers; the older brother, Ryuuichi, who's an high school student and his younger brother, Koutarou, who is a toddler.
Due to a tragic event, Ryuuichi and Koutarou lose their parents, but they're taken in by a gruff older lady lovingly called "Obaa-san" (grandmother) and her butler, Saikawa.
Ryuuichi has to work in the "babysitting club", a club where teachers from the school drop off their children, as exchange for living with and studying in Obaa-san's house/school and the manga follows the adventures started in this club.

The story is very simple, but does it's job extremely well. Every chapter is very cute and has episodic stories with reoccurring side characters, references to previous jokes and running gags, etc. etc.
You'll find yourself satisfied with each chapter as they're all very fleshed out and leaves a sense of "ah, that was a good story" every time you complete one.

The art is cute and simple, it fits the story of the tone well with it's shoujo manga-esque art style, round toddler faces and exaggerated (to a natural extend) expressions. All the characters are easy to distinguish and identify from one another.

All the characters has a good and a bad side, which makes them seem all the more real. The main character, Ryuuichi, is a hardworking guy who loves his brother, but can also be extremely dense and an airhead, which sometimes causes him trouble as well.
All the children are written realistically to the extend that they're believeable, but you won't get annoyed by their irrational antics, fights, etc. as the characters and their "motivations" are often easily understood and related to.
All the side characters are great too and aren't just dismissed randomly after a few chapters. Even the characters who only show up once in a blue moon go through character development of some sorts, or at least get some kinda of backstory to understand them better.

Overall this is a great slice of life manga with a great cast, cute story/stories, a warm atmosphere and it leaves you with a sense of belonging and familial love.