I just received an invitation to my twin SISTER's PPD that is being thrown by her FI parents. The wedding is in 2 1/2 weeks but the PPD is in July. His parents addressed my invitation to Ms.bananasplit and FIancee. I can't help but be a little offended because this is my sister's PPD we are talking about. Couldn't they have written the name of my FI? Is this proper etiquette and I am just offended for no reason?