In the series, it is stated that Kakashi was 26 when he became the leader of Naruto's squad. So following that, he was 14 when the Kyuubi attacked the village. Seeing that Obito was the same age as Kakashi, he should be 14 but he didn't look like it. How old was Obito at that time? It shows him as an grown up, adult man. Is this because of Zetsu covering him or is he just older than Kakashi?
This is not a question directly about the age of Obito but also why he looked older. In my understanding Kakashi and Obito are about the same age. I don't care when Kakashi became a Jounin because that is not relevant to this question.