Siblings of [name_m]Jakob[/name_m] I have heard of are
[name_f][/name_f][name_m]Felix[/name_m], [name_f]Phoebe[/name_f] and [name_f]Delia[/name_f]
[name_f][/name_f][name_m]Felix[/name_m], [name_m]Jacob[/name_m] and [name_m]Max[/name_m]
[name_m]Felix[/name_m] and [name_m]Henry[/name_m]
[name_f][/name_f][name_m]Felix[/name_m], [name_f]Greta[/name_f] and [name_m]Francis[/name_m]