Now I know a lot of people are going crazy, organizing the facts we have been given regarding Tobi, and finding plot holes regarding Tobi's age and stuff. SO first let's get down to that.
We'll be using Kakashi as our reference age because we can assume that he and Obito are the same age because they were on a team together. So as of now Kakashi is 30 years old.
Tobi has done many things through out his life which include:
- Giving Nagato his Rinnengan
- Convincing Yahiko to form Akatsuki
- Controlling Yagura, the Fourth MizuKage
- Attacking Konoha and Stealing the Ninetailed-Fox
- Aiding Itachi in the Uchiha Massacre
Whether you believe it or not Kishi has made it very obvious that it is Obito who was under the mask, however it does not explain how Obito, who is roughly 30 years old, could do all those things, especially when most of these events occurred 16 years before the start of the series, when he was 14. For example, giving Nagato the Rinnengan. Nagato was the apprentice of Jiraiya before he took on Minato as his apprentice, way before Obito became a shinobi. Also Yagura was Mizukage while Zabuza was an academy student. That is when Kirigakure was called the Village of the Bloody Mist and had the tradition of killing your fellow classmates to graduate. Zabuza and Kakashi are the same age Obito could not have been Tobi at that time. However in present time, Tobi removed his mask to show Kisame who he really was and Kisame recognized him? :/
So how is this possible? Well if you recall, Tobi once took on the identity of Madara. I think that Tobi has been several different people and Obito is the current Tobi. I think those who assume the identity of Tobi all share the ideal of The Moon's Eye Plan. Madara even mentions the Moon's Eye Plan to the Tsuchikage during their battle (Ch. 562, Page 4)
I think that Uchiha Madara was the founder of the identity of Tobi and was the very first Tobi. This explains how Tobi had the Rinnengan (which was awakened by Madara before his death). However that means that there must have been other people who acted as Tobi before Obito and after Madara. They have access to many Sharingan (Ch. 482, Page 482). This would explain how Tobi would have certain Sharingan powers at certain periods of time. To conclude think of Tobi as an ideal, not a person. He is many people who share the same vision and those people include, Madara Uchiha and Obito Uchiha. I hope this helps