You can take back a previous surname, if you can prove in your application that it used to be your surname. Certain restrictions apply if the applicant got the previous surname with the consent of a husband or wife, or ex-husband or ex-wife.
Eva Svensson used to be married to Sven Lind and was then called Eva Lind. After their divorce, Eva took back her maiden name, Svensson. However, Eva has two children with Sven and the children's surname is Lind. Now Eva wants to have the same surname as her children, so she applies to PRV to take back her ex-husband's surname.