Ar tonelico II: Melody of Metafalica

Cloche, Croix, Amarie, Luca

Croix, luca ,Cocona, Jackly

Croix - Cloche and Amarie - Jacqli
I suggest Amarie even though she and Jacqli only have "good" relation because she is a support character that can heal a lot.

Leglius-Cloche Croix-Jacqli
Jacqli Songs are jus the best on my opiniom, and Cleche especially for Replakia(don really know if this is the right name) but her song magics are nice too and very funny xD

Croix and Luca ? and Jacqli. I prefer Luca and Jacqli in a group together regardless of who the Vanguards (thing that's the correct name) are. Both of their song magic(s) are rediculously strong.