I thought [name_m]Ludo[/name_m] was quite rare. Neither [name_m]Ferris[/name_m] nor [name_m]Ludovic[/name_m] seem startling or out of place with siblings. I think when names are a lot more unusual, the scope for cohesion tends to be a lot wider.
[name_f][/name_f]A few ideas:
[name_f][/name_f][name_m]Melchior[/name_m]
[name_f][/name_f][name_m]Emrys[/name_m]
[name_f][/name_f][name_m]Faraday[/name_m]
[name_f][/name_f][name_m]Laertes[/name_m]
[name_f][/name_f][name_m]Erasmus[/name_m]
[name_f][/name_f][name_m]Amias[/name_m]
[name_f][/name_f][name_m]Leopold[/name_m]
[name_f][/name_f][name_m]Bartleby[/name_m]
[name_f][/name_f][name_m]Jovian[/name_m]
[name_f][/name_f][name_m]Ephraim[/name_m]
[name_f][/name_f][name_m]Sylvan[/name_m]
[name_f][/name_f][name_m]Ulysses[/name_m]
[name_f][/name_f][name_m]Taliesin[/name_m]
[name_f][/name_f][name_m]Dorian[/name_m]
[name_f][/name_f][name_m]Lazarus[/name_m]
[name_f][/name_f][name_m]Arturo[/name_m]
[name_f][/name_f][name_m]Horatio[/name_m]
[name_f][/name_f][name_m]Jolyon[/name_m]
[name_f][/name_f][name_m]Lysander[/name_m]
[name_f][/name_f][name_m]Tybalt[/name_m]
[name_f][/name_f][name_m]Emilian[/name_m]
[name_f][/name_f][name_m]Ozias[/name_m]
[name_f][/name_f][name_m]Balthazar[/name_m]
[name_f][/name_f][name_m]Quillan[/name_m]
[name_f][/name_f][name_m]Theseus[/name_m]
[name_f][/name_f][name_m]Ingram[/name_m]