Why is Jon Snow the rightful heir to the Iron Throne?

I don't get this, how come son of Rhaegar Targaryen is the rightful heir to the Iron Throne when Viserys was declared Mad King's heir?

Rhaegar was Viserys’s older brother and the heir. The throne would only pass to Viserys if and when Rhaegar andall of  his children were dead. Queen Rhaella was not aware of Jon’s existence and so she crowned Viserys at Dragonstone.Jon is alive,He’s Rhager’s eldest surviving son(According to the show),that put him above Viserys and Daenerys inthe line of succession.Viserys was never the true heir.However if we go by the books then neither of them are the rightful heirs its Aegon VI(Jon would be Aegon VII if his name is Aegon in the books)

Originally posted by: Anastasia69

Rhaegar was Viserys’s older brother and the heir. The throne would only pass to Viserys if and when Rhaegar andall of  his children were dead. Queen Rhaella was not aware of Jon’s existence and so she crowned Viserys at Dragonstone.Jon is alive,He’s Rhager’s eldest surviving son(According to the show),that put him above Viserys and Daenerys inthe line of succession.Viserys was never the true heir.However if we go by the books then neither of them are the rightful heirs its Aegon VI(Jon would be Aegon VII if his name is Aegon in the books)

Aerys (Mad King) has said that Viserys is his heir, at that time Rhaegar's son Aegon Targaryen VI, was living in the KL with him, so even if they didn't know about Jon Snow, Rhaegar's line was pushed out of inheritance. Viserys declared Daenerys his heir, so technically Daenerys is the rightful heir to the Iron Throne.

Jon Snow took the oath of Night's watch, so he can't be the King, He bent the knee in front of Daenerys, she is his queen. 

Last King was Robert Baratheon, his son Gendry is there as well

Because of the Dance of Dragons(A massive war between brother and sister for Iron Throne)women were kicked to the back of the line of succession to the Iron Throne and could inherit only when all other male claimants died.So not only Jon any other Male Targaryen be it uncle or cousin they would’ve have better claim than Daenerys.

And for Jon “I shall live and die at my post.”He died as lord commander,So he is free of all the Night watch’s vows and Oaths.

North was never his to give away,Sansa is the rightful heir.Jon is the rightful heir of the seven kingdom so basically he bended the knee to himself.

Daenerys can never be rightful heir as long as Jon lives,No matter who declare whom the heir.Jon’s claim would beat Dany’s regardless just going off post-Dance of the Dragon succession, just because he’s male and she’s female. The fact that he’s the offspring of a first born male means his claim would trump hers even if he was a woman.

Originally posted by: Anastasia69

Because of the Dance of Dragons(A massive war between brother and sister for Iron Throne)women were kicked to the back of the line of succession to the Iron Throne and could inherit only when all other male claimants died.So not only Jon any other Male Targaryen be it uncle or cousin they would’ve have better claim than Daenerys.

And for Jon “I shall live and die at my post.”He died as lord commander,So he is free of all the Night watch’s vows and Oaths.

North was never his to give away,Sansa is the rightful heir.Jon is the rightful heir of the seven kingdom so basically he bended the knee to himself.

Daenerys can never be rightful heir as long as Jon lives,No matter who declare whom the heir.Jon’s claim would beat Dany’s regardless just going off post-Dance of the Dragon succession, just because he’s male and she’s female. The fact that he’s the offspring of a first born male means his claim would trump hers even if he was a woman.

1 King Aerys declared Viserys as his heir when Rhaegar's son Aegon Targaryen the VI was in his custody, so offspring of first born was ruled out of succession by order of the King. 

2 Jon didn't bend the knee to the throne or house Targaryen, he bend the knee to Daenerys, he gave up his claim to the Iron Throne, this is what Sam told him, he did not know about his parents but he did bend the knee, so men/women or anything does not work here because Jon already claimed Daenerys his queen 

3 Even if Jon is an heir to the throne, Gendry has equal claim as he is the son of last King. 

4 When Daenerys believed that she was the heir to the throne, she built an army to get it back, Robert Baratheon won't hand over Viserys or Daenerys the throne because they are Targaryen. 

My point was that the situation or rules in Westeros are not what they were before Robert's Rebellion, everyone had equal claim to the throne and the expectation that Daenerys has to give up, just because Rhaegar was shameless enough to leave his kids and wife without protection, to marry another woman, is not correct