Is it permissible to marry a half-brother with the same father?

According to Point d, Clause 2, Article 5 of the 2014 Law on Marriage and Family, the following acts are prohibited:

Marriage or cohabitation as husband and wife between people with direct blood relations; between people within three generations of kinship; between adoptive parents and adopted children; between former adoptive parents and adopted children, father-in-law and daughter-in-law, mother-in-law and son-in-law, stepfather and stepdaughter, stepmother and stepson;

And Clause 18, Article 3 of this Law stipulates: Those who are within three generations of kinship are those who share the same origin, including parents as the first generation; siblings who share the same parents, the same father but different mothers, the same mother but different fathers are the second generation; first cousins are the third generation.

Therefore, you and your lover have a relationship as siblings with the same father but different mothers, which falls within the second generation, so you are not allowed to marry your current lover.

Note: If you and your lover still marry each other, you will be fined from VND 10,000,000 to VND 20,000,000 according to Clause 2, Article 59 of Decree 82/2020/ND-CP for the act of: Marriage or cohabitation as husband and wife between people with direct blood relations or between people within three generations of kinship;

Best regards!