If your forced into it and it's not your fault fine. Please don't choose to Merry your sister. That's just wrong. It's not 1590 anymore and we have enough people. Please just please don't choose to merry your brother or sister. They shared a womb, they share your DNA and they share your parent(s)
The scientific truth says that this is not right. We, as humans, are not made to mate with our close family- that is why their is rules. Offspring can have a number of problems, other than just being "inbred". It is unsafe and and unruly practice that cannot happen, especially when the goal is to produce offspring.
Its basic human nature to fall love with people, and regardless of who that is, you should be able to be happy. However my argument is that although they should be able to be wedded, they should not have children due to the fact that a great deal of "inbreads" come to have a genetic defect/ mutation when born.
To summarise they should be able to get married however, although im not 100% against it, re production between them should not be a factor
Incest, like any act (sexual or otherwise) has the potential to be immoral should it produce harmful consequences, such as if a defective child were created as a result of the union. However, it is easy to conceive of a situation in which this is not the case, e.g. two adult siblings engaging in contraceptive sex. Thus, incest is not always wrong.
If two people have the same recessive disease the chance of it being inherited is 100%. But there are no laws about those two people getting married, much less having sex.
The chance of there being a disease from brothers and sisters having children may be more than the average but it is far less than 100%.
Also marriage=/= having children. There are plenty of childless couples.
Look at it. The brother and the sister could be monks and nuns. You don't have to forsake marriage and romantic love to be a good person or to love God ( they are not the same). The question never specified that they were even biologically closely related. Therefore, it might be alright for them to marry!
If two people capable of consenting are in love, then I don't see any problem with it. The main argument against incest is the problem with children, but if they agree not to have children then where is the problem? Also if they do, does that child have less right to life than any other child?
I think that so long as they are in love, and it is consensual, incest and incestuous marriage is harmless.