It's funny; the third volume seemed to anticipate some of my complaints from the first two volumes. It starts off with the protagonists marveling at the differences in gender on the human world, in comparison to the relative lack of genderedness in their species. They decide to try being girls for a bit, and one of them seems to prefer it, until misogyny gets in the way.
Still, that wasn't enough to win me over. In the end, I would say that this series is just OK, and I would advise readers to try "Hirayasaumi" instead, which I personally found much more enjoyable. In "Tokyo Alien Bros," the tone is somewhat ominous, even though it tries for humorous. The contrast between the two brothers is interesting, because the one who seems kind and cheerful has a hidden darkness/emptiness to him, while the brother who seems stiff and grouchy ends up having a heart of gold. I prefer the grouchy brother myself and found him to be much more sympathetic throughout the series.
The third volume does include a fair number of moments that feel climactic, which is nice for a finale. But overall, this isn't one of my favorite mangas. I'm glad that I gave it a try, but it just didn't resonate with me.