Fealty might be for determine periods (generation, two generations etc.) or perpetual. In both cases signiferus keeps their name with addition to fealty. Unlike adoption, fealty is applied for a whole Familia, not only a single member.
Form of address:Lord / Lady [full name] de Familia [fealty family name]
Lady Virginia Potts de Familia Stark ; Lord Erik Selvig de Familia Foster ; Lord Lars Heimdall de Familia Odinson