It is responsible for people to act upon genetic sexual attraction, as it is a natural and common thing in today's society. As long as the people practice safe sex, and are relatively careful. There are some things that should be taken into account. As in if the person is married or in a commited relationship, then it can be irresponsible.
People are here scientifically speaking for only one reason, and that is to pass on their genes so that their species continues on. So there is nothing wrong to act upon genetic sexual attraction, it is why you are here, and it is your instinct to want to have sex.
In general, the genetic sexual attraction is something that they cannot help and does not hurt another person. Yes, there are limits, but, in general, there are going to be attractions between two consenting adults, and that is perfectly fine, as it doesn't directly harm anybody else. As for acting upon genetic sexual attractions, sexual attraction is generally a perfectly natural and normal part of human life.
Genetic sexual attraction is simply gross and awful all the way around. It's called incest and it's illegal. There is no place for such evil in contemporary society when there are so many people on this planet to be attracted to. It is completely irresponsible in today's world to act upon incestual feelings towards a close relative.
Genetic sexual attraction is something that was studied in regards to adoption. In this setting researchers found that when a child is adopted out to a family and then later runs into family members (unknown to them) that they could be attracted to them because of their similarity. Of course it would not be responsible for people to act on this attraction, but it is a problem associated with adoptees as they do not know who their genetic family is.