There are some people who should never look attractive to you no matter how they look. Examples of these set of people are your mother, father, siblings, cousins or other family members. You people are family and you all share the same blood.
They are your kin and you should never have any form of sexual relationship with them. God doesn’t want it and He has made it clear in the Bible.
There are some countries that allows you to marry your kin or family members and people actually follow that which is really bad. Do you know what makes it very bad?
It’s because they have disobeyed the law or what God has said and followed the rule of a mere human maybe their president or whoever gives them access to do that.
In the Bible, Leviticus 18:6-9 says; None of you shall approach to any that is near of kin to him, to uncover their nakedness: I am the LORD.
The nakedness of thy father, or the nakedness of thy mother, shalt thou not uncover: she is thy mother; thou shalt not uncover her nakedness.
The nakedness of thy father's wife shalt thou not uncover: it is thy father's nakedness.
The nakedness of thy sister, the daughter of thy father, or daughter of thy mother, whether she be born at home, or born abroad, even their nakedness thou shalt not uncover.
This is the warning given to us in the Bible by God. Never let the nakedness of your family member trick you to do something funny which God has said no to.
It is not good to have any sexual relationship with your family member. If you do it, on judgement day, this act will be judged by God.