Lincoln's Boys

[L Verge]

This is an off-the-wall question, but has any historian studied the relationship of Hay and Nicolay to Robert Lincoln? I have heard that the three were friends, but for some reason, I have wondered whether Abraham Lincoln's close relationship with Hay and Nicolay ever had any effect on Robert (i.e. jealousy). I might toss Elmer Ellsworth into the mix also. There was some age difference, I believe, but not enough to preclude Robert being envious of the time and respect that his father had for these three men.