Q. 1. Are Catholics allowed to marry a relative?
A. 1. Marriage in direct line, such as father-daughter, grandmother-grandson, is never permitted in the Catholic Church. This is called the impediment of consanguinity.
The reference to this fact is found in Canon Law # 1091 where it states:
§1. "In the direct line of consanguinity marriage is invalid between all ancestors and descendants, both legitimate and natural."
§2. "In the collateral line marriage is invalid up to and including the fourth degree."
§3. "The impediment of consanguinity is not multiplied."
§4. "A marriage is never permitted if doubt exists whether the partners are related by consanguinity in any degree of the direct line or in the second degree of the collateral line."
Marriage between first cousins may be dispensed by the Bishop.