姉妹
Shimai
Things and people from Japan are Japanese.
my sisters
and i
my sisters hair is brown.
It is grammatically incorrect to say sister and sister. You just say sisters.
la chambre de ma soeur
se that how you say sister
Sisters is the plural form of the word sister. For example you could say: "I have two sisters." Sisters' refers to the possessions of those sisters. For example you could say, "My sisters' beds are beautiful" by which you mean that the beds of both of your sisters are beautiful.
"Mes deux soeurs" is how you say "my two sisters" in French.
"Sisters forever" is "hermanas para siempre".
my twin sisters is mes soeurs jumelles
Seven sisters are "sept soeurs" in French.