How can I know if the person I am in love with have my same sexual orientation?

I'm bi-sexual myself and there was this one girl that I really fancied, however, I didn't know if she was straight or into girls like me. So I wondered how I would be able to find out whether she was of the same sexual-orientation. It turns out she was bi-sexual (but she had a boyfriend sad times) and I found out by just talking to her and watching her actions. She acted a lot like I did and I definitely noticed her checking out a few girls and then during the middle of a conversation it cropped up that she was Bi so I asked her and she said yes. Most people don't actually mind being asked what their sexual orientation is so if you're confident then just go ahead and ask! If not you may have to do a bit of research on the person you're in love with.

The only way to be completely sure is if they tell you. Don't assume peoples sexual orientations as you can often be wrong.

The only way to truly know is to ask them! You can be upfront and ask them or you can ask about their past relationships.

The best way to find out is to bring up the topic in casual conversation, at least this was you know if they are super supportive or against your orientation.

Communication is important. You can't assume somebody's sexual orientation without them stating their preferences or sexuality. You can try to base it on stereotypes but that is not a good way and can cause problems. Talk to them or others that know more about them.

It's simple. Ask they person. If you are shy, ask indirectly. Ask about their likes and dislikes, ask if they ever had a girlfriend or boyfriend, you will easily get to know.