Not much to say here, except that Russian does not have a special word for siblings or grandparents.
Unlike English, Russians rarely say "my mother", "my grandfather"; usually they omit "my".
...And when they don't, it is more natural to use reflexive "свой" (one's own). English does not have anything quite like that. Essentially, it is a substitute for my, your, his, her etc. that you use when it refers to the person (or thing) that is the subject of the sentence or, at least, the clause you are in. A few typical examples:
Forms of «свой» follow the same mostly-adjectival pattern that «мой»,«твой», «ваш», «наш» and «этот» use: свой, своя, своё, свои → своего, свою, своих...
Since «свой» describes something belonging to the subject of the sentence, it cannot be used with the subject of the sentence itself. The exception is made when you are making generalisations, e.g. "One's (own) reputation is always more important"~«Своя репутация всегда важнее».
Pay attention to what the grammatical subject is. Sentences like «Мне нравится у своей сестры» are sort-of-OK sometimes, but you are really treading on thin ice here. This one sounds almost normal, while some others would immediately look unnatural.
In spoken Russian «дядя»(uncle) and «тётя»(aunt) are often used to refer to some adult "guy" or "woman". A special case is children's use, since they often use it even as a form of address ("тётя Маша!").
This course doesn't cover this. But it's still useful to know.