This picture was taken by some friends who recently got married. The assumed writer is actually someone with a degree in writing, so I am guessing that this was written either by their spouse, or by one extremely sleepy writer.
It should actually read, "The Griffins." In this instance, it is not possessive. You would need an apostrophe for such a phrase as, "The Griffin's home." To just state the couple in a plural manner, there is no need to be possessive. There is also one other small problem with this envelope. Until has an extra L. Like I said, this came from a talented writer, so it is very much a goof. But, regardless of who wrote it, there can always be a lesson to be learned.
*If you feel like doing some Grammar Goof sightseeing and live in the Springfield, MO area, drive by the Battlefield and National intersection. On the North side of the intersection, there is a school bus for the Springfield Public Schools, with a sign saying you can apply "On Line." I certainly hope the sign doesn't speak for the Springfield Public School system... I will post it, if I can ever get a clear picture.