Daytime barking is bad enough, but nighttime barking is unacceptable if you have close neighbors. I, personally, think that the dogs must be kept indoors, at least during the nighttime hours to avoid them being a nuisance to the neighbors (of course, I couldn't sleep either if mine were barking). I don't know how your brother gets any sleep either if they are barking. Our 4 are kept in every night, whether we are at home or not. My petsitter comes and lets them inside, and then comes back the next morning to let them out when we have to be gone overnight. A couple of them prefer to stay in all the time!

I would take a neighbor's complaint really seriously, as they probably have some grounds to call animal control if the barking is excessive, especially during the nighttime hours. Sure wish I had a suggestion to "fix" the barking issue, but they are either bored or very curious of everything that they see (that's the way mine are).

Good luck.
Logan