I think there is a 'tipping point.'

Everyone in a relationship is attracted to some other people. They don't need to mention it; it goes without saying.

But in the past, a lot of gay guys had gfs and this was partly just because of social pressure. If they could have had a bf, they would have. They were nowhere near evenly bisexual.

Same with a lot of BLs.

So if you're sure your attraction to boys is just a secondary quirk in your sexuality and you can easily live without dealing with it (other than knowing that you're a normal person and not a freak - now you know), then you don't need to tell the girl even if you marry her. It's just one of those expected, unspoken other attractions.

If it is in some way pressing for you, or if it's the major component of your sexuality (for example, if you've had a drink or two and you j/o, you almost always 'get wicked' and think about boys because they are actually the biggest turn-on), then you're not going to be able to just treat it as nothing. It's a significant part of you.

In that case, you better find some relatively safe way to let her know before you marry her, or before you marry whoever you marry. Or before you make another serious commitment like having a kid together.

I know a guy who fell asleep in front of the computer and his wife came in and saw he was logged onto a boy site. Their marriage survived. Another college student had his gf barge into his residence room as he was kneeling on the floor jerking to a boy photo ... that relationship survived too. Women mostly just want to be sure that they are number one and that you won't hurt any kids. You better be sure both those things are true before you have this discussion.