I know in some cultures they say you should “cover up” in front of your dad but you father and brothers are your mahram so my question is are you allowed to wear normal pyjamas at home such as short tops, shorts etc ? What should the limit be to this as your family at home are all mahram

The clothes should be appropriate. Pajamas and such are acceptable. So a girl must not wear something too revealing or provocative in front of her male family members.