I would name a sister to [name_f]Matilda[/name_f] “Tilly”…
[name_f][/name_f][name_f]Eleanor[/name_f] nn [name_f]Leni[/name_f] (or nn [name_f]Nellie[/name_f], if he still likes it as a nickname)
[name_f][/name_f][name_f]Adeline[/name_f] nn [name_f]Addie[/name_f]
[name_f][/name_f][name_f]Harriet[/name_f] nn [name_f]Hattie[/name_f]
[name_f][/name_f][name_f]Dorothy[/name_f] nn [name_f]Dottie[/name_f]
[name_f][/name_f][name_f]Josephine[/name_f] nn [name_f]Josie[/name_f]