Am I the only one who think that incest is happened when 2 or more people doing it if they...

Step stuff isn't an incest like step brother but step father is an incest... ( we're talking about yaoi?) if you're talking morally normally people wont fall in love with father,mother,brother,uncles and aunts and in some cultures cousins... and morally step stuff. But personally I like yaoi with step brothers and I can't see it as incest.

The only way it can be called incest is if one of your parents' remarries and has a child together. Say your mom/dad has you and 1 sister/brother and the other person has a son/daughter from previous marriage, it wouldn't be called incest. If you've watch soaps, that would be exaggerating, but somewhat true when the story lines' created in that way. However, ex. if your mom has a kid with your step-dad, that child would be your half-brother/sister and it would still be consider incest that child would have half your blood relation and that would be risky.

I think step-relatives depends. I mean, if they're 18 and have been step siblings since they were 5, that's a hell of a lot difference if they're 18 and have been siblings since they were 15. Cousins I'm okay with since, while it's frowned upon in my country and even illegal in many places, I understand that it's considered acceptable in some places. Step-parents I have a problem with since they married their spouse and promised to be a father/mother for their step-child. To me, a romantic and/or sexual relationship between them, to me, seems like a betrayal to both the spouse and the child.

But there are people who fall in love with their parents, even if they are exceptions. I've read about the fact that some girls who grow up without knowing their fathers fall in love with them, once they get to know each other. In some cases, they even engage in relationships. Awkward, but ¯_(ツ)_/¯

Thanks for the answers!

So., if a child has a romantic relationship with their step-parent., it still counts as incest, even they're not blood related?

Legally, no, but if you ask me I would say yes.

And distant relatives is also fine with me. Well, it kind of has to be, considering my grandma married her third cousin, lol.

In some places and at some times first cousins are considered okay. I'd get genetic counseling before having kids though. One set of my great-grandparents were first cousins and my grand father was completely color blind.

Surprisingly it's ok if you've got an illegal child who doesn't know about you, later on you 2 can marry. It may sound stupid. but take a moment and think, he's got a child never seen and finally they meet they don't know they're daughter and father and got married? Laws wont forbid this relationship to continue.. So I think in cases like these where people don't know they're blood related and fall in love is just to let them be.
And as stated above, being step brothers /sisters when you're 5 not like when you're 18...Personally someone I'm growing up with will be like a real brother so no as well.
Step parents/ sons and daughters in law are well, idk personally.

You mean if the name of the parent isn't on the birth certificate? I'm pretty sure that would still be illegal. At least, it would be in my country. Oh well, different cultures, different customs I suppose, lol.

lol how would anyone know? I mean and illegitimate child you don't know of and he/she doesn;t know of you. And the papers doesn't say you're related and you don't know you're related... later on it was found out, so you'd just let them be or separate them?

Ooooooh, that's what you mean. An Oedipus incident, lol. I've actually heard of a situation where the husband and half the town knew his wife was actually his daughter. Everyone knew but her.

Wow, I never heard of an actual case, but I'm saying theoretically even if it's incest if people didn't know about it before hands let them be

In the case I mentioned, they did know they were blood-related beforehand, which is the problem. But different from @LessThanThree's case, only both sides of the family knew about their situation. I found an article with more detailed info
http://www.dailymail.co.uk/news/article-2915094/I-lost-virginity-d-never-felt-comfortable-man-Daughter-plans-marrying-father-talks-taboo-relationship.html

One word... Disturbing.

What the hell, New Jersey? No. That's how you get baby's with terrible, life ruining disorders. Bad New Jersey. Bad. No cookie for you.

Also, as someone who's basically a daddy's girl despite being an adult, I find this especially disconcerting. He shouldn't be having kids. We've already seen what happens when he does that. Even if the baby doesn't have a disorder, it's just wrong. Oedipus thought it was wrong. When a guy in Ancient Greek mythology has a better sense of reasoning than you, there is a problem. XD

IMO a father who marries his daughter is selfish enough, I don't think he will think about stop having kids and spare them diseases and stuff...

Poor girl was brainwashed. It's terrible the friends and family didn't try and stop her. I feel bad for the mother, too.