Sissel is a blonde Nord girl child that can be adopted in Skyrim: Hearthfire, along with her twin sister, Britte. Sissel is the younger sister (by five minutes).
Britte, her sister, is often arrogant and cruel towards her younger twin, saying things such as "You can beat up my sister if you like" and "My sister's not even worthy of standing in my shadow." It is also possible her father beats her.
Sissel can only be adopted if her father, Lemkil, is dead