Does anyone have any good advice for when problems with other students makes training feel bad?

First, my dojo situation: it has three "branches" that meet at community gymnasiums in different areas, with only a handful of people in each branch. We can go to any of these branches, but are generally considered to be associated with one and its sensei. Our branch is relatively new, and besides sensei there is only one black belt and two browns in addition to the white belts.

Second, people: recently the black and brown belts in our branch have been unable to come to practice. Most of the other white belts don't come much and haven't made much progress. Almost every training session is me with a family of three: father, mother, and junior-high-school son.

They are nice enough people, but...the father can be pretty annoying--he laughs when other people do something wrong and continually tries to correct others incorrectly. I don't mind being corrected, but it's just confusing when it contradicts what sensei says. Plus, the father only started a few months before I did.

The mother is now pregnant and can't really do much.

The son is not really a challenge to do kumite with, and to make it worse he will sometimes basically fall asleep or totally lose concentration (look at the wall or ceiling) while sparring!

Lately training just isn't fun anymore, so I have been thinking of going to another branch once a week even though I like my sensei and it would be farther to travel. The people there are mostly black/brown belts and I get along with all of them. But I would basically have to make up a white lie as to why I had to go to the other branch on another day.

I think "having a talk" with my sensei is just not the Japanese way and would make me seem selfish. I also think part of training is to be able to do one's best in any situation, so don't want to feel like I am "running away."

Anyway, thanks to the forum for letting me get this off my chest...and anybody ever have any similar situation or advice?