Id have to go with Japanese, along with other cultures families(I would think), do teach the older generation to protect the younger and adult males are know to fawn over there daughters as adult females over sons, same for most cultures. But the way the boy acted is not anything so unusual, if you had to compare then define japan as a society with more restraint in behavior than others.
As for the older generation my anime experience is crap, stuff about unrequited love from sisters towards brothers young or old... complete crap(though there was that one article about that voice actress with her very underage brother). But from the least biased animes, they're no different than an American sibling pair, maybe closer and more attuned to each others feelings(the American portray of sibling rivalry doesn't fit well). Family bonds are nurtured more in Japanese societies than American after all.