Yikes. Sounds like a case GSA- genetic sexual attraction. It's up to you two to decide what to do, especially since there isn't even a tiny chance of children. Look at laws for your area, etc.

I would do a second test. Maybe some cross contamination of your samples happened.

First I would check pretty carefully to see if the information is accurate before making any decisions. Second, if it is true I would not freak out about the situation. The chances of there being an actual issue in possible children from both having the same father (if it’s true) are generally way overstated. Get expert advice if it’s actually true - not from family and friends.

If you two really love each other, i say screw it and get married if you want. Maybe not make any kids for fear of increased chance of defects, but there is always adoption and the choice is up to you. Like others said, do a second test first though, but in the end, you only just found out and that shouldn’t have to stop you

I think the best unwritten part of the FML is knowing that at some point, one of them got the impulse to compare parentage, like they perhaps suspected something was up.

And now I guess it makes more sense when you look back at the family gatherings, where both you and your partner called the same man "dad"..

If the OP & his sister (including 1/2 siblings) live in the United States, all 50 states classify marriage, sexual intercourse, and/or cohabitation as illegal. Every state, except Rhode Island, has penalties that range from up to $100,000.00 and prison time. In 4 states, the penalty is life imprisonment.

Well... I mean, you made it this far, and clearly one of you didn't know your father, so you weren't raised together. I...don't really see anything wrong with it? It's not like you're adoptive siblings or something, you didn't know about the other person hahaha. I'd just keep it to myself and not let it affect me tbh. Don't throw away an eight year relationship over something like that just because you now know.

I'm rather certain that OP is also a woman, given their name in this post. Also, in some locations it would in fact be illegal for them to remain a couple with knowledge that they are half siblings. Which means they need to find that out, because punishment depends on location.

So come up with a royal family crest get married and say your family is well royal....