User blog comment:Gumball2/The "Sister"/@comment-31563773-20170707134348

If they went with the bunny idea, they'd have to come up with some really good excuse as to why almost half of those 25 kids weren't male, because there's a high chance between litters that the genders will be more diverse.

As for the show, I'm not sure if this is due to lazy writing and more due to the fact the writers only have 11 minutes to try to include as many characters as possible, so when they want to use the girls, they're forced to find the easiest way to include all of them. While it's apparent that the whole 'sister' concept happens when it's something against Lincoln, the girls themselves can be more selfish towards each other, since this can cause them to fight over trivial things. The fact they don't like being a lone is an interesting concept, though I wouldn't say they wouldn't care if he gets hurt (since they go overboard when he gets extremely minor injuries). Also, I'm not sure if the girls are too afraid to stand up to each other, cause they sure fight a lot.

One thing I'd like to point out is the possibility that the girls are jealous of Lincoln to a degree. Being the outnumbered sibling, he has to stay a few steps ahead of them, especially if it's something he wants: reason for this being that the girls would want the same thing, or try to enforce their opinion on him. A few episodes you lsited prove this, as well as Dance Resolution and The Sweet Spot.