Not available for Romanian. In Romanian it is only gemeni, no matter the number of them. From Latin gemini.I think that Latin and the Romance languages qualify.
Another formal word in Chinese is 孪生子 (孿生子). 孪 itself contains the meaning of "twin".Mmm... Not sure how Chinese would be viewed here, since in Chinese twins are associated with the idea of pair, which I supposed is related to two, but not exactly. Anyway you decide whether or not it fits.
双胞胎 (Mandarin: shuang bao tai; Cantonese: soeng baau toi) - twins (双 means pair)
孖生仔 (Cantonese: maa saang zai - dialectal) - twins (孖 is a dialectal word for pair)
I would like to add, in case somebody don't know, that 雙胞胎 can be also the name of a food in Taiwan.双胞胎 (Mandarin: shuang bao tai; Cantonese: soeng baau toi) - twins (双 means pair)
Hungarian: iker [now no relation with two, but originally 1000 years ago there was, Turkish iki, eki]
No, the Spanish name Iker is actually Basque (not a "natural" name, but one created by Basque writer and nationalist Sabino Arana).Is it related to Spanish name Iker?