At the beginning of in ספר במדבר chapter 3, the Torah states, ואלה תולדות אהרן ומשה, "And these are the generations of Aharon and Moshe." The next verse, however, proceeds to list only the sons of Aharon: אביהוא, אלעזר, ואיתמר נדב,. Why does the first verse introduce the next posuk as listing the sons of Aharon and Moshe, if the next verse does not even list the children of Moshe?
Rashi cites Chazal, who say that if someone teaches Torah to someone else's child, then it is as if the child is his own. Rashi subsequently explains the next part of the first posuk mentioned here "the day that Hashem spoke to Moshe on Har Sinai" because it was on that day that Aharon's sons became the "sons" of Moshe as well. This is because it was that day that Moshe taught them what Hashem had said to Moshe.
But shouldn't Moshe's children also be written here? After all, they were his sons too. A possible answer is that since Moshe was so busy taking care of the nation he was not able to take care of his own children's education. In Sefer Shemot (91:41) the Torah relates that "Moshe went down the mountain to the people."
Rashi comments there that Moshe did not head home, but rather went to the people and tended to the needs of the nation. Therefore, Aharon's sons had earned the title of being Moshe's sons (since they studied Torah with him), while Moshe's biological sons did not.
When the father is not able to teach Torah to hi son, the Rebbe is sometimes to be treated with even more respect than the father (see Baba Metzia 33a). Yet Aharon the father is mentioned before Moshe the Rebbe in the pasuk! An answer is that Aharon too taught Torah to his children, so he was mentioned before Moshe.
The Rambam (Guide to the Perplexed 1:7) explains that when a pupil gains knowledge from his Rebbe, then it is as if the Rebbe has fathered the pupil, because the Rebbe is the "owner" of that knowledge.