Similar in what ways? The odds of two languages in different parts of the world being significantly similar, with no historical relation or contact between them, is very low. I definitely can't think of any.

Certain parts of languages might appear superficially similar. For example, the syllable structure of Hawaiian and Japanese is similar--most syllables consist of a consonant followed by a vowel, and there's no consonant clusters in a syllable. But the possible consonants/vowels are nothing alike, the grammar/syntax are nothing alike, and the words have nothing in common either.

Another place where languages might appear similar on the surface is if they have a few words with similar meanings simply by chance (called "false friends"). For example, English have and Spanish haber "to have" appear very similar, but actually aren't related at all. (even though Spanish and English are in the same language family) For a crazier example, how about English "man" and Mandarin 男 nán "man"?

At any rate, while two languages may have unexpected similarities in some areas, there's no cases I can think of where two unrelated languages have these kinds of similarities in enough areas to really call them "similar" overall.

Not sure this is really a historical question, but I hope this helps.