I've been doing a lot of research on this topic, but I have found little clues. People say that Obito and Rin are about 4 years older than Kakashi, but I don't think that's true.
People keep saying that it's proven in the manga and the show, but as far as I know that is not true.
That's completely wrong. If they were indeed 4 years older than Kakashi, they should have been a lot taller than him when they were part of Team Minato.
Anyway, it's not said exactly how old they are, but judging by the fact that most ninja students become a Genin or get graduated at the age of 12, and since these are the birthdays of the characters:
there are some scenarios we could come up with (imagine the world of Naruto being 2005 and 2006):
All three of them are born in the same year, making them all the same age (12) and making their age order like this: Obito>>Kakashi>>Rin, making Obito 7 months older than Kakashi and 9 months older than Rin, while Kakashi being 2 months older than Rin.
They are born in different years: making it look like if Rin is born in 2005 and the other two in 2006, then it's Rin>>Obito>>Kakashi, making Rin only 13 years old, while Kakashi and Obito are 12, and are 10 months and 3 months younger than Rin, respectively.
If you mean the current timeline, obviously Rin is dead, but Kakashi was 26-27 years old in part 1, and 29-31 years old in part 2, same for Obito. This will automatically make Rin 29-31 years as well, if she was still alive.
It makes perfect sense that they're 4 years older than Kakashi. If you become a genin upon graduating the academy and the 3 of them graduated together. That means they're older than Kakashi by atleast 4 years. Kakashi became a genin at 5 while Obito and Rin were 9 meaning they were 4 years older than him when they all graduated the academy.
No. They were all of the same age. They were classmates. Kakashi was made the genin much earlier owing to his skills, whereas Obito and Rin joined him later. In episode 385 of Naruto Shippuden, Obito clearly mentioned "but he is the same age as we are" (from the past memories).
I think Kakashi is older than Obito because just like Naruto, he is clumsy like Naruto and as we know, Naruto is younger than Sasuke. So, I think that Obito is younger than Kakashi and Kakashi acted more like Sasuke doing all of his work like Sasuke. So, I think Kakashi is older than Obito.
