Hi Doll,
That is currently how our family reunion is set up. In 1992, when my cousin organized the reunion, he made it a reunion of his maternal side and his paternal side.

When he was organizing the reunion, I heard that he encountered negative feedback. Some cousins in his maternal family were not familiar with the people in his paternal family, and felt that the reunion was not really formed for the entire family but just his immediate family members. He encountered some of the same feedback from some members of his paternal family, I was told. Of course, you can always expect some type of negativity when planning a reunion, whether it's a two-family reunion or an one-family reunion.

Because my cousin's maternal family, of which I am a member of, is much larger than his paternal family, the reunions have been vastly attended by his maternal family. Also because of the increased participation from his maternal family, the participation from his paternal family has been decreasing. One thing you have to consider in having two-family reunions is that not everyone will be blood related to each other, and if the reunion is mostly attended by one side, some members of the other side may start to feel alienated.

The reunion will likely still be a success, but there are certain things you will have tackle when you are dealing with two different families coming together as one. You have to carefully plan the programs, making sure that both families are equally represented, or you will encounter negative feedback. Also, you have to make sure there is equal representation on the committees, fundraisers, etc.

These are just my personal experiences.

Melvin