I adored him like an older brother.
This word consists of kanji with hiragana attached. Because the hiragana ends with an う sound, you know this word is a verb. The kanji itself means yearn for, so the verb version is to yearn for. But that sounds kinda old fashioned, so you can just use to adore too.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You didn't learn that reading with this kanji, so here's a mnemonic to help you:
You realize you're starting to yearn for someone way more than you used to. "Sh*t (した)... " you say to yourself. This wasn't supposed to happen. Anytime you start to adore someone like that you always know you're getting into a bunch of sh*t you don't want to deal with. Damn these emotions!