Here are some other ideas...
J+U: Joshua, Jude, Judah, Judith, Julie, Julia, Julian, Justin, Justine
J+G+R: Jagger
G+U+F: Gustaf
G+R+F: Garfield, Griffin, Griffith
U+F: Rufus, Rudolf
G+R: Edgar, Gabrielle, Gabriella, Gabriel, Gary, George, Georgette, Georgia, Georgina, Garret, Garrison, Garth, Geraldine, Gerald, Gloria, Grace, Greta, Grover, Gordon, Margaret, Grady, Graham, Grant, Grayson, Roger, Brogan, Bridget, Craig, Regina, Morgan, Regis, Virginia
G+R+U: Gertrude
R+U: Arthur, Drusilla, Bruce, Cyrus, Darius, Raquel, Ruby, Trudy, Marius, Raul, Ruben, Rudy, Ruth, Russell, Ursula, Wilbur, Uriel, Thurston, Stuart, Murray, Luther, Laura, Maura, Hunter, Curtis, Courtney, Aurora, Audrey
Also, the one letter Jeffrey and Guy they have in common is Y, so maybe a Y-name (in honor of that connection) would suffice.