He should have been older.

He should have grown up with Owen (actual brother or brother-in-law or at least close enough to be an "uncle" to his son), who thought Anakin shouldn't follow Obi-Wan on some damn fool idealistic crusade.

Basically, the prequels make Obi-Wan into much more of a liar than he originally appeared to be. According to ROTJ he only lied about the identity of Darth Vader, not all the other stuff. That's helped by him actually looking uncomfortable on that line reading.

I also guessed back then that there would be a real or imagined love triangle between Obi-Wan, Anakin and Luke's mom that would be the basis of their conflict and mistrust.