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Those names have pretty similar sounds, so I don't think most of them could be combined as first + middle name.

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Emilia and Liana have prominent "li" syllable and "a" ending
Emilia and Elena have the same beginning and ending and similar "li" and "le"
Elena and Liana have the same syllable pattern, same ending, and similar "li" and "le" (also "len" and "lian" are a bit similar)

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Celine is your best bet for a name you could combine with the others.

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Emilia Celine could work, they both have "li" but the emphasis is different enough to pull off.
Elena Celine, maybe not because the "len" and "line" are both emphasized and too similar (if you're pronouncing it eh-LEN-a that is). Celine Elena is too matchy, it ends up sounding like "se-leena-lenna".
Liana Celine could work, the "li" syllables do match but they're split up a bit. Celine Liana wouldn't work as well because the "li"s are right next to each other, and both are followed by "n" so you get "line-lian". (Also, I just noticed the Lian part of Liana rhymes with Dion so it sounds too much like Celine Dion.)