Family is what you make of it in Heart of a Samurai. There's blood family, yes, but then there are also all the people Manjiro meets along the way as he travels from Japan to America and back again. Plenty of them become family, too, particularly Captain Whitfield and his wife and child. So though Manjiro longs to return to Japan—and ultimately does—this winds up seeming less like choosing between families in some ways, as embracing an expanded idea of family.
Questions About Family
Which is Manjiro more loyal to: his Japanese family or his American family?
What's the connection between food and family for Manjiro?
What makes a family a family?
How does guilt figure into Manjiro's relationship to the people he loves?
Chew on This
Ultimately, family boils down to blood no matter how much Manjiro loves other people.
Family isn't all about blood for Manjiro; it's about common interests and time spent together.