The Twins Who Were Seperated at Birth

two girls kaitlyn and alexis have been in the system for there whole lives and their 16th birthday is coming up and they don't have anywhere to go but where they are with separate foster family's and no biological family.. they have been friends since they were 4 but no one but the social workers know their secrect.. they don't even know it.. because they were brought into the system seperatly by different people. these girls grew up thinking they were sister because how they treat each other and how their birthdays same day same year. could these two be twins?