It depends on your family’s opinions, I guess. In some cultures it’s fairly common to marry cousins. Sometimes people will marry their late sister’s husband for example.

I also know a couple who married. They were step brother and sister and raised together as siblings from being teens, then married. They were not blood relatives.

Second cousins are legal to marry.

The illegal reason for not marrying first cousins is because the genetics mixing can damage the baby.

“Cousin couples have only a slightly higher incidence of birth defects than non-related couples. 26 states allow first cousin marriages; most people can marry their cousin in the US. US prohibitions against cousin marriages predate modern genetics. No European country prohibits marriage between first cousins.”