Of course there are words for parents, siblings, uncles, aunts, cousins, grandparents, etc. It's slightly more awkward to refer to second cousins, great uncles, and in-laws, but that's not really a problem.
However there aren't any simple terms in the English language for relationships like my cousins' cousin's granddaughter, my second cousin's cousin, someone's significant other, or a son-in-law's sister and I consider all those people part of my family even though the way they are related to me may be complicated. If I see them at family gatherings they're family to me.
Eventually my husband came up with a term that applies to all of those and any other convoluted relationships. He called them "step-neighbors-in-law" and now I do, too.
Do you have any step-neighbors-in-law?