I wanted pretty sounding names, and because their last name is short I wanted their first names to be longer (so they wouldn't have a "blunt blunt" type of name). I wanted classic names that had some dignity to them, and names that would serve them well both when they were children, but also when they grew up (and if they grew up to be in powerful or prestigious positions). In other words, I didn't want (for example) my baby daughter to grow up to become a physician and be something like, "Dr. Fairy-Princess Smith". lol
I also wanted both of their names (my younger son's and my daughter's) to have some sense of elegance to them - I guess because I hoped that kind of name may help my children had just a hint more self-respect than they might have if they had a silly (or otherwise unappealing) name.
My eldest son came with a first name because he was adopted in infancy. It was a long, ethnic, name. I shortened it in order to make him feel more as if he fit into our "ethnicity" (which is "melting pot" essentially). I didn't want to take away "the main part" of the name given to him by the birth mother, so I gave him my father's first name as his middle name - my way of his having something from the birth mother, something from my side of the family, and his last name from his father/my husband. My younger son's both his father's first name as his middle name, mainly because it sounds good with his first name. My eldest's son very short first name sounded prettier with my father's longer first name (which doesn't have the same consonent in it as my eldest son's first name). So, as you can see, a nice sound of the first- and middle- names together mattered to me.
(There's a few consonants that, if repeated too many times in someone's name, don't sound good to me. :/ )