John (my cousin) & Jane (cousin-in-law)

When sending a letter and writing their names on the envelope, which is correct?

1. Cousin John & Cousin Jane
2. Cousin John & Jane

I would think #2 is correct because I don’t have to repeat the word “cousin” because they are both my cousins, but I don’t want Jane to feel like I don’t consider her a cousin because I didn’t write “Cousin Jane” so in that case should I just write Cousin John & Cousin Jane?