He's your second cousin and most people would think it okay if you date him.
Your great-uncle is your grandparent's brother.
Your great-uncle is therefore uncle to one of your parents.
Your great-uncle's kids are therefore first cousins to one of your parents.
One step down from each generation there's you, and the child of your first cousin who you are dating-- your boyfriend is therefore your second cousin.
In most cultures of the world it would be considered okay to date and even marry your second cousin. It is rarely illegal. Some societies have an expectation that relations should be kept more remote; for instance, if you are Sikh, then it would be prohibited for you to marry any but the most distant cousin.
Under Sikh rules, that would make Queen Elizabeth of Britain and Prince Philip's marriage prohibited, as they are both descended from Queen Victoria and about third cousins to each other.
President Franklin Roosevelt was married to and had many children with his second cousin, Eleanor. It's not that uncommon. You might want to think carefully if you have any genetic disorders in your family, though.
Your great-uncle is your grandparent's brother.
Your great-uncle is therefore uncle to one of your parents.
Your great-uncle's kids are therefore first cousins to one of your parents.
One step down from each generation there's you, and the child of your first cousin who you are dating-- your boyfriend is therefore your second cousin.
In most cultures of the world it would be considered okay to date and even marry your second cousin. It is rarely illegal. Some societies have an expectation that relations should be kept more remote; for instance, if you are Sikh, then it would be prohibited for you to marry any but the most distant cousin.
Under Sikh rules, that would make Queen Elizabeth of Britain and Prince Philip's marriage prohibited, as they are both descended from Queen Victoria and about third cousins to each other.
President Franklin Roosevelt was married to and had many children with his second cousin, Eleanor. It's not that uncommon. You might want to think carefully if you have any genetic disorders in your family, though.