Adopt a Kantian or Rawlsian perspective of 'limited interchangeability'.
Since any of us might have been any other one of us, humans are ends-in-themselves and not mere means. Therefore circumstances that reduce them to mere means-to-an-end should be avoided altogether when possible, and otherwise shaped so that status can be embraced willingly in a way that allows the person in question to value themselves as highly as any other being.
First of all, I am going to define sex very narrowly as unprotected, potentially reproductive activity. The rules for all related activity are generally derived by reference to that narrow definition. But they are not the same thing, and rules about them do not necessarily have the same moral basis.
From that perspective, you can argue that forbidding sex entirely is unacceptable because extinction is not a desirable outcome. Even if the nonexistence of humans is a neutral state, achieving it by gradual attrition would be a painful lot for the last survivors. Since none of us would want to be one of those people, and we can prevent that suffering, we should. Some people should breed.
None of us would want to be a rape victim, or to be faced with the choice of giving up a child we had just invested nine months worth of effort into producing, (unless we had willingly decided to do so from the beginning.) To the degree that these states can be avoided, they should.
We also would not want to be an unwanted child. To the degree this can be avoided, it should. So sex should take place in a way that maximizes the odds the parent or parents who end up with the child will not resent it. This implies that they accept responsibility for the child freely, (or that they find it more suitable parents.)
Biology and the psychology of bonding can take care of this. But by not establishing this decision before risking producing the child, one is needlessly increasing the risk that it won't. Romantic love tends to make selfless obligation more tolerable, so although it is not absolutely necessary, it is clearly helpful.
So, from this perspective people should breed. They should endeavor to do so in a way that does not produce rape or abandonment or resentment of their children. This is most likely when they accept commitment to form a family, and is best maintained in the case when they appreciate one another.
This is not equivalent to any version of what is asked, but I think it may be the closest fit that I would not declare either offensively false, or just plain meaningless.
If you want more restrictions, you are commanding someone as to what use they can put their body, without adequate warrant. Almost any additional logical restrictions make the person into a means-to-an-end, with that end being the stability of tradition or manipulating the odds in a game of biological determinism.
If you want greater coverage, you are treading on forcing values derived by the straight culture for its own ends, during a period when women generally did not live to menopause, onto everyone else. There is no particular reason for the sterile, by nature or contrivance, to avoid sex without commitment, especially if it is a variety of sex that does not spread disease. The bad fit of the advice to the audience then just makes it meaningless.