Hello,
I just want to be clear on this before I try to move on. Are these correct?

The acquaintance (friend) is male:

Брат моего (g.c.) знакомого (g.c.) должен приехать в Москву (a.c.). - My friends brother is supposed to come to Moscow.

The acquaintance (friend) is female:

Брат моей (g.c.) знакомой (g.c.) должен приехать в Москву (a.c.). - My friends brother is supposed to come to Moscow.

сестра not yet discussed in Pimsleur but:

The acquaintance (friend) is male:

Сестра моего (g.c.) знакомого (g.c.) должна приехать в Москву (a.c.). - My friends sister is supposed to come to Moscow.

The acquaintance (friend) is female:

Сестра моей (g.c.) знакомой (g.c.) должна приехать в Москву (a.c.). - My friends sister is supposed to come to Moscow.

Thank you,

Scott