Re: How would you pronounce these names??
I think Regan and Reagan tend to be pronounced differently, the former as REE-gin and the latter as RAY-gin.
However, with Keagan and Teagan, I would deviate from this pattern and pronounce both with a long E sound (KEE-gin and TEE-gin). I went to high school with a girl named Teagan who pronounced it this way.
Of course, I'm ready to be corrected on the proper pronunciations of any of these names if I've gotten them wrong.