Negative Mitzvah 340
Prohibition against marriage with one's father's sister
Leviticus 18:12 "Do not act immodestly with your father's sister"
It is forbidden to take your father's sister (your aunt on your father's side) as a wife.
Negative Mitzvah 341
Prohibition against marriage with one's mother's sister
Leviticus 18:13 "Do not act immodestly with your mother's sister"
It is forbidden to take your mother's sister (your aunt on your mother's side) as a wife.
Negative Mitzvah 342
Prohibition against marriage with one's uncle's wife
Leviticus 18:15 "She is your aunt; do not act immodestly with her"
It is forbidden to act immodestly with your uncle's wife (your aunt because she married your uncle).
Negative Mitzvah 343
Prohibition against marriage with one's daughter-in-law
Leviticus 18:15 "Do not act immodestly with your daughter-in-law"
It is forbidden to act immodestly with your son's wife (who is your daughter-in-law).
Negative Mitzvah 344
Prohibition against marriage with one's sister-in-law
Leviticus 18:16 Do not act immodestly with your sister-in-law"
It is forbidden to act immodestly with your brother's wife.
Negative Mitzvah 345
Prohibition against marriage with two sisters
Leviticus 18:18 "Do not marry a woman and then take her sister as a wife"
It is forbidden to take a woman as a wife when you are already married to her sister.