My mother had scar tissue removed so she could conceive. She was 36 at the time. I was born when she was 38, and I'm the oldest. Genetically speaking my younger sister is the pick of the litter.
My mother was hoping I'd be twins, as her father had been one. Please don't do what my great grandparents did, and name the twins Edgar and Edna. (They were going to call granddaddy Edbert, so it could have been worse!