Clearly you have little or no understanding of constitutional law and most certainly have not read any of the court cases leading up to the SCOTUS decision, leave alone the Obergefell opinion (if you even know what that is) I will paraphrase from memory from the majority opinion:
“ Same sex couples will now be afforded the same rights that opposite sex couples enjoy in accordance with the laws of the state in which they reside”
No state allows for the marriage of close relatives of the opposite sex ( except for a few shit hole red states that allow first cousins to marry) and therefor the ruling does not allow for the marriage of any close relatives.
Same sex couples won the right to marry because-after protracted legal fights at the state and apelet levels, culminating the SCOTUS decision, the opponents' of same sex marriage were never able to articulate a compelling state interest-or even a rational basis – for banning same sex marriage , The high court concluded that same sex couples – comprised of consenting adults who were not closely related- were essentially the same as heterosexual couples.
It does not take a genius to understand that a parent marrying an offspring or siblings marrying poses a whole new set of legal and social issues that would have to be decided on their own merits. Such arrangements would upend the concept of marriage and family to a far greater extent than same sex marriage.
Without passing judgement on the concept- I will just say that if a father wants to marry his daughter- he is free to pursue that issue through the legislative or judicial process just as gay people did. However, it is likely to prove more difficult to show that there is no compelling government interest in prohibiting such a union.
So much for your idiotic red herring and slippery slope logical fallacy bullshit