Weddingbee boards

I am addressing the last of my std's and I am stuck on this one envelope.  Here is the story, my stepdad's uncle passed away earlier this year leaving behind his wife and son.  The son, my step dad's cousin is in his 40s, and he moved back home because his mother was having a hard time coping.  They are both invited to the wedding.  Since they have the same last name, I do not want the envelope to come accross as they are married.  Do I put their names on different lines? Do I send two separate STDs?

Here is an example address to make giving an example easier of y'all. :)

Mr. Cousin  Mrs. Aunt    123 Main St.  Augusta, GA 12345

Thanks guys

Thank you, that helps.  One last question, should I put her name first or does that even matter?