In college I was friends with a guy and a girl. They later became a couple. You could say I got them together. They became the sickly sweet couple who finish each others sentences and believe they are perfection bestowed unto the world. Spending any amount of time with them causes your brain to melt into a puddle. Years passed and we socialised every few months and kept in touch. Then, the girl took offense to some imaginary slight I apparently made when they were first dating and decided she no longer wanted me in her life. I kept in touch with the guy and made a few olive-branch attempts to mend the rift with the girl, to no avail.
Today, I received an invite in the mail to their wedding, postmarked 2 days previous. Their wedding is in 3 weeks.
How do I go about politely declining this invite, which makes me feel like they need a warm body to fill seats? Once upon a time I considered both to be my closest friends so I don't want to be rude.
Any advice on how to handle this situation?