"Είμαι μεγαλύτερος από την αδελφή μου."
Μετάφραση:I am older than my sister.
"elder than" is not correct: As adjectives, they are only used before a noun and you cannot say “elder than”: my older/elder sister. the older/elder of their two children. I'm the oldest/eldest in the family.Dec 16, 2013 Elder brother - English Language & Usage Stack Exchange english.stackexchange.com/questions/.../elder-brother-or-older-brother
there is no reason we can't say I am bigger (in height etc) than my sister.
I liked also the explanation given here http://www.dailywritingtips.com/older-vs-elder/ ..."Elder is descended from the Old English word eldra, which refers to a parent or other older person."
Also on Wordreference forum why we should avoid to use "elder than"...http://forum.wordreference.com/showthread.php?t=1666846