What is the حد (prescribed punishment) for incestuous adultery? And is there repentance from it?

Incest is a greater sin than fornication with non-mahrams. Some scholars have gone so far as to rule that the perpetrator should be killed unconditionally, whether married (muhsan) or not. This is one narration from Imam Ahmad, and Ibn Uthaymeen chose it. However, the majority view is that the punishment for incest is the same as for regular fornication: stoning for the married (muhsan) and lashing for the unmarried. The severity of the sin of fornication varies and is multiplied depending on the circumstances, such as if the woman fornicated with is a mahram, or a wife, or a neighbor, or the wife of a warrior (ghazi), or if the fornicator is married (muhsan), or if the act occurred in a revered place or time. Whoever is afflicted by this must hasten to repent to Allah, for repentance is accepted no matter how great the sin.