I wouldn’t give the vowels or syllables another thought if it was me. It’s possible to find incidental patterns with just about anything. So while it’s nice to find a pattern, I question if it’s worth limiting the names you have for consideration or settling for a name you might not truly love. I prefer to look at sibling cohesion in terms of overall style, familiarity and balanced meanings. Here are some suggestions taking [name_f]Emrie[/name_f] and [name_m]Odin[/name_m] as inspiration:
Annika, [name_f]Anya[/name_f] or [name_f]Anouk[/name_f] as variations of [name_f]Ann[/name_f], [name_f]Linnea[/name_f], [name_f]Frida[/name_f], [name_u]Zola[/name_u], [name_f]Saskia[/name_f], [name_f]Inez[/name_f], [name_f]Minna[/name_f], [name_f]Delta[/name_f], [name_f]Fia[/name_f], [name_f]Calla[/name_f], [name_f]Sabina[/name_f], [name_f]Zelie[/name_f], [name_f]Pippa[/name_f], [name_f]Audra[/name_f], [name_f]Libby[/name_f], [name_f]Selah[/name_f], [name_f]Cyra[/name_f], [name_f]Lera[/name_f], [name_f]Djuna[/name_f]
Raphael, [name_m]Cassius[/name_m], [name_m]Tobias[/name_m], [name_u]Ari[/name_u], [name_m]Maxim[/name_m], [name_m]Linus[/name_m], [name_u]Axel[/name_u], [name_u]Tate[/name_u], [name_u]Griffin[/name_u], [name_m]Leif[/name_m], [name_u]Blaise[/name_u], [name_m]Magnus[/name_m], [name_u]Rex[/name_u], [name_m]Casper[/name_m], [name_u]Amos[/name_u], [name_m]Tybalt[/name_m], [name_m]Conrad[/name_m], [name_u]Wiley[/name_u], [name_u]Roscoe[/name_u], [name_m]Lars[/name_m], [name_m]Nikolai[/name_m], [name_m]Viggo[/name_m], [name_u]Mack[/name_u]