There was less than a year between them, a year that had flown by so that their mother sometimes forgot which was the elder of the two, and indeed most people found it difficult to remember. The eleven months were not used as a tool to gain superiority, but forgotten about. They played at being twins, and there was only ever one birthday party for the two Evans girls, halfway between the two dates. The neighbours suspected it was out of convenience, not knowing that it had been the girls' request, and that they couldn't bear to be thought of as different from one another.
They shared a room and a bed, the two strawberry-blonde heads side by side on the pillow. On cold nights they curled into each other, two slender figures melding into one. Their father was mildly concerned, and their mother reassured him that they'd grow out of it, though the words began to sound hollow after her suggestions that they each have their own room had fallen on deaf ears.
It was a relief when Lily went off to school and Petunia stayed behind. Hogwarts had done what they had not been able to do – separate the girls. Despite the miles between them, hours were devoted to reading and writing long letters, a desperate attempt to bridge the distance between the two worlds. Petunia refused to make friends with the girls at her school, insisting that she already had a sister, who was so much better than a mere friend, and so when Lily came home for the summer, chattering of the friends she had made throughout the year, it came as a shock to her.
The letters were few and far between the following year. Lily returned with hair redder than it had ever been before. It was something to do with magic, she explained in between talking about her teachers and classes and friends, and it was only then that their parents noticed how the red had faded from Petunia's hair.
Petunia herself made the connection some time later, and saved up her pocket-money for a trip to the chemist's. When she emerged from the bathroom with jet-black hair that evening, her parents murmured something about it being a phase, and she hated them for not understanding.
By the third summer there was no chance of anyone pointing out a family resemblance between the two girls, let alone anyone describing them, in jest or seriousness, as twins. They celebrated their birthdays on the appropriate dates, and Lily had her own bedroom for the months she was at home. Once, on a particular chilly night in mid-winter, Petunia wondered whether Lily had anyone to curl up with at that school of hers, but she quickly banished that thought from her mind and her dark head soon sank into the pillow.