I was wondering where Toto's family(tribe) is as well but they might have all been slaughtered, think about the time period that this Manga takes place. Sad but absolutely something that happened at the time, whole tribes slaughtered.
Not all the tribes were" slaughtered". Many Native Americans live on their own lands, run by them own by them. the U.S gov, must ask permission to arrest any one on those lands. The u.s gov. holds in trust something like 3.4 bill. that they keep tract of for all the rental rights on these lands. A lot of killing happened on both sides in the 1850 war in the west. The Wind Talkers (forgot which tribe) were used in WW2 for their code work. The code was never broken.
Not all of them were slaughtered but a lot of them were and it's very possible that his tribe was slaughtered and/or scattered. Also the US government is known to ignore it's own rules when it's inconvenient for them. Taking into account the time period that this takes place I'm going with his people are dead.
P.S Before you think I'm some foreigner slamming the US, I'm American.
I thought it was real cute but where is Toto's tribe? Did he get banished? I wish it would've went more into his backstory. Also during both Toto's and Fran's talks Fran kept saying he couldn't understand or that Toto couldn't. But they both answered each other's sentences perfectly.