There are 4 types of consanguinity (ญาติทางสายโลหิต) that the laws prohibit the person to get married:
1. the direct ascendant line which is a father, a mother, a grand parent, a grand mother. For example, the daughter cannot get married with her father.
2. the direct descendant line which is a child, a grandchildren, great-grandchild, and child of great-grandchild. For example, father cannot get married with his niece, mother cannot get married with her son, or grandparent cannot get married with grandchildren.
3. brother or sister of the blood relation of the parents. For example, brother cannot get married with his sister.
4. brother or sister of the blood relation of the father or the mother. For example, brother cannot get married with sister of the different mother.