Going to my cousin's wedding and I'm 'still' single? Advice on how to deal with the old biddies?

I find your question somewhat contradictory. You are saying you have a fantastic life, but on the other hand, you feel "lonely" when you're around your siblings who are married, have families, etc. Well, what ever the case may be, you don't need your aunt's approval to live your life the way YOU want to live it. Perhaps you can drop by at the wedding. Just "make an appearance" but don't stay long enough for people to comment on your lifestyle choices. Furthermore, my husband always advises me to wear my "I don't give a sh!t" tattoo on my forehead when going to family gatherings! There will ALWAYS be somewhere out there who gossips about you and disapproves of your decisions. As long as you are happy, that's all that matters.