Possessives in the Dative

After the dative prepositions mit, bei, von, zu, aus, nach, seit and after verbs such as helfen, gehören, gefallen, danken, gratulieren, the possessive takes the dative ending:

• masculine and neuter: -em, as in meinem, seinem, unserem (mit meinem Bruder = with my brother)
• feminine: -er, as in meiner, ihrer, unserer (bei ihrer Tante = at her aunt's)
• plural: -en, as in meinen, euren, and the noun also adds -n unless it already ends in -n or -s: mit meinen Freunden (with my friends), bei meinen Eltern

As in the accusative, euer loses its second e before an ending: eurem, eurer, euren. Remember that es geht also takes the dative: Wie geht es deinem Vater? (How is your father?)