Unrelated languages that share a border can start to share grammar too
Albanian, Romanian, Bulgarian and Macedonian belong to different branches of the Indo-European family, yet centuries of contact in the Balkans left them sharing grammatical features none of their close relatives have, like tacking the definite article onto the end of a noun instead of in front of it. Linguists call this a 'sprachbund,' a language area bound by contact rather than ancestry.