Valentine Twin Ponies
White baby earth pony with red mane and tail, red and pink rainbow over a red heart symbol
AND
Purple baby earth pony with pink mane and tail, first tooth, pink heart with lavender arrow through the middle
I don't really know why these are twins, since Hasbro's twin theory generally involves some feature in common, but nonetheless, this is who they are. One eary rumour named the white one as Red Rainbow, but, although this is a cute and popular name for her, it has not been officially confirmed. In fact, they do not appear to have been given actual names of their own. They were released through a stationery company offer of some kind, I think - they were not available in the UK.