This animation is pretty good, I personally like the way the characters move.
Now this doesn't mean the animation isn't flawless, and I don't mean the drawings. The music were at times, music I've heard before, and that's not a terrible thing, but when music is overused like one specific track used, it just gets to me. The character's voices are another problem I have with it, around 4 minutes in the characters get unusually loud which is an issue with the quality in my opinion.
Now the characters are pretty badly designed in my opinion. The first and second brother I can get behind, but the third is just awfully structured, the only thing I've been irritated by is his constant saying of the word "What?" it's repetitive and gets annoying quickly, not to mention how brother two can say something quietly, only to have brother 3 jump in sound volume and have me turn down the volume.
Besides my issues with the sound of the animation, the story was slowly paced and hard to really follow due to the low volume of the characters in the beginning, and the plot twist at the end came out of nowhere. Not once in the story is a 4th sibling even mentioned.
I guess the only good thing I can say about this is the animation is really lively and the facial emotions are displayed openly and it's very smooth. I do enjoy the few visual gags that I noticed and most of the characters look original in their own way.
Out of all of this I have to give this animation 3/5