About 6 months ago, my son Eliot (14 years old) made an interesting comment. At least my wife thought it was interesting. He said: Dad, if I could do it, I would invent a time machine, so I could go back in time and be your brother. Leaving aside the technical difficulties left unaddressed by his statement, I have to admit that it touched my heart in a powerful way.
It made me realize that in many ways, I already thought of my son as my brother. Since about the time he was three years old, our thoughts have been very congruent and in phase. Even though Eliot is adopted, he is much more like me (in many ways) than I am like my own brothers.
Another reason Eliot wants the time machine is that he feels he missed out on the best parts of the 20th Century (1950s and 1960s). He is very nostalgic for certain eras which he never lived through himself. This YouTube video shows one event that Eliot would like to go visit in his time machine: