Yeah, I knew about most of that.
Most people don't realize that most of the time, it's the marriage that is illegal, not the act.
For the Alabama one do you mean the act is a felony? or marriage? (To my knowledge it happens more in florida, so kinda funny that alabama is known for it despite not being one of the most common places).
The link has a table that gives info on each state. In Alabama incest is a Class C felony. There are some states where incest is punishable by up to life in prison while others it's like 2yrs/$500. The reason Alabama is mocked so often is that not only are Rednecks not protected they are an Approved Target Class. I think this constant mocking, particularly by those in the liberal coastal urban areas who also mock everyone in "Fly-over Country" (look how red that is on an electoral map outside of Illinois where only Chicago matters), is one reason that the region tends Republican (the Fuck You All effect).
(All of this below is from the Wikipedia page linked in my original comment.)
Some state very narrowly define incest so you can get away with just about anything. An example of this is Florida, where incest is "sexual intercourse" which is defined as "the penetration of the female sex organ by the male sex organ, however slight". Another example is Maryland, where "vaginal intercourse" is illegal. So in those types of states you can lick/suck each other or bone your sister's ass all you both want.
Counter to this is Massachusetts where what is illegal is "Marriage, sexual intercourse, sexual activities (including but not limited to, oral or anal intercourse, fellatio, cunnilingus, or other penetration of a part of a person's body, or insertion of an object into the genital or anal opening of another person's body, or the manual manipulation of the genitalia of another person's body)". So there I guess all you can do is masturbate in front of each other.