paro

Paro is a word of quantity, so what it counts follows with da: paro da okuloj, paro da ŝuoj. Use de only when you mean possession, which with a pair you almost never do. The word covers both a matched set of objects and two people who go about together, and for the second sense geedzoj is the married version if you want to be specific. Parigi is to pair things up and pariĝi is to pair off, the -ig- and -iĝ- pair doing their usual work.