The Swedish Norwegian connection...twice!

My hobby is researching my roots. My mother is from Norway and my father is from Sweden.
My cousin on my mother´s Norwegian side he married a Swedish lady who also is researching her family tree. So I and my cousin´s wife have a hobby in common. One day she contacted me and said: - You know what!? We are relatives which she found out when she compared our family trees.
- No, you are kidding! It turns out that my mother´s family also married someone from my father´s family. Again! I mean how likely is that!? Really!?