Моя is singular. Моя сестра. My sister. Мої is plural. Мої сестри. My sisters.
I'm very confused when to use моя and when to use мої. I thought it was a gender thing, but мої сестри doesn't follow the pattern i expected.
"мої" is used in plural situations while "моя" is used in singular situations. In this case it would be "мої" because it is saying sisters instead of sister or "сестри" instead of "сестра."