He's about 18, is it possible that the Sandpoint Kaijitsu's were gone by then, but that other members of the family were still there? Don't remember if the whole family made a run for it, or just part of the family.
All of them. Ameiko's grandfather was the only survivor. Lonjiku and Ameiko were born in Varisia, Lonjiku probably in Sandpoint, Ameiko definitely.
Also, the Kaijitsus were originally from Minkai, on the opposite side of Tian Xia from Goka. Goka IS the closest city in Tian Xia to Avistan, though.
If you want to have some fun with it, you can work with a variant I'm using in my RL game:
Since you asked, I'm going to shamelessly link to my player's kitsune's background. (Read Shiro's background.) Without having read Jade Regent, I wrote the entire thing based on web research, the Inner Sea World Guide, and stuff I made up whole cloth.
But it's a nice, "How do you get a kitsune bard from Minkai into Sandpoint?" story that might give you some ideas.
The closest thing the Kitsune have to a "homeland" is the Forest of Spirits, which is to the north of Minkai and connects the Minkai peninsula to the rest of the continent. However, the Forest is not a "nations" so much as a wild land with lots of fae, kami, and other things living there.
The Kitsune are also minorities in several other nations, including Minkai. Other nations include Kwanlai (opposite Minkai across the Aya Maru, the sea separating it from the mainland), Amananadar, Shokuro, and also Hwanggot and Quain. Amanandar is the interesting one for this character as it is ruled by Taldans, and a visit there might have inspired a desire for this character to visit the west.
The trick is that Minkai is on the eastern coast of Tian Xia and your Kitsune character would have had to cross the entire continent to get to Goka.
Kitsune tend to be wanderers, and a dissipate Kitsune bard is a lot closer to the Kitsune norm than a hard-working shopkeeper. They fill the same niche in Tian Xia that gnomes fill in Avistan. So if you want to stick with the disapproving father background you could say that the Shiro's father had an obsession with "fitting in" to human society and felt that drawing attention to the wild nature of typical Kitsune (who may be distrusted by many humans since they are shape-shifters) would lead to prejudice and persecution from humans.
Getting from Tian Xia to Avistan is a tough journey and there are two routes. The land route is across the pole, the "Crown of the World," and while this route seems pretty insane to me it does basically connect Minkai and Avistan pretty directly, so aside from the Arctic wastes Shiro would not have had to visit too many other places to get to Varisia.
Going by sea is trickier of you are coming from Minkai. Theoretically one could circumnavigate Tian Xia by going around the southern end, but this is apparently very dangerous and is not done by commercial ships. The other way would be to cross Tian Xia by land. You could get a lot of the way by boat by coming through Benchu Bay to the Sea of Ghosts (a north-south oriented sea in the middle of the continent). At the north end is the Gan-Tzou river that leads to Amanandar (which is inland). At the south end the sea is fed by a river that separates Po Li to the south and Lingshen to the north. Lingshen is a militaristic human-only empire but Po Li would probably be a bit more welcoming. On the river in Po Li is Changdo, the traditional capital of the great Empire of Lung Wa (which has been shattered into successor states) and would be a reasonable place for a "tourist" to wish to see.
West of Po Li is Quain, another country with a Kitsune Minority. From here Shiro might go the south coast where Quain connects to the western ocean via a long unnamed bay; from there he might have caught a ship to Goka and then to the west. Or perhaps he would have travelled along the Golden River which constitutes the border between Quain and Lingshen; from the headwaters there might be a wroute through the mountains that links Quain and Goka directly; otherwise a quick jaunt through Lingshen would be necessary to reach the pass that leads to Goka. From there ships travel to Vudra; a ship could have gone around the south end of Vudra, up the narrow sea between Garund and Vudra, past Jalmeray and Absalom, and through the inner sea to the ocean and up the coast to Varisia. This is a very long sea voyage.
If you want to limit the number of places Shiro has visited then you should probably have him take the land route. The sea route would mean that he is truly world-traveled.
Peet