We sent out our invites a few weeks ago and started receiving RSVPs last week. We sent them so early because my mother in law was bugging us about it because some of her brothers were bugging her about it since it's across the state from most of the family.
This morning my fiance's uncle from Nevada (we live in Illinois) called to say 5 out of the 6 we expected from his family were coming. Okay, no big deal. I was at work so I couldn't stay on the phone to ask
who wasn't coming. My fiance texted him to ask, so we have the seating chart right.
The uncle said his two oldest children are a maybe because they're 17/18 years old so it's up to them whether they want to come. Okay, no big deal. But he said if the two oldest kids don't come he wants to bring his two college friends who live in a town 70 miles from us, who said they could stay at their house instead of staying at a hotel. So he's basically already invited these friends.
How do I politely say "you may not bring your college friends. The invitation was for your family. We are not inviting people we have no relationship to when our guest list is currently 150 people." We gave plus ones to 99.5% of guests, just not the teens in high school (mostly kid free wedding other than first cousins and newborns), and most of the guests are my fiance's family because he has a large Mexican family. We only invited aunts, uncles, first cousins, and a few friends, and the uncle's nine siblings plus their spouses will be at the wedding, and his wife too, so it's not like he won't know anyone at the wedding.