Yes, he says the same thing. I'm fairly sure it's not the first time Himawari has used "daisuki" regarding the boys.

From my experience talking to people and what I know of the culture, aishiteru is almost never used. Even married couples don't generally use it. I think it's considered "too much" to actually say to somebody. (Off the top of my head, the only time I remember hearing it used in anime is ones aimed at girls with very romantic themes, like Fushigi Yuugi, or only the woman uses it.) Just about everywhere, it's "daisuki" or "suki" no matter how epic the love may be (like Sakura and Shaoran.)

I'm far from the end-all-be-all on the culture, but that's just what I know.