Is it ok to love your step-sister and ask her out and eventually marry her?

Despite the narrow minded idiots of the internet, there is no just reason for it to be wrong to have a crush on, or fall in love with a step sibling. Even if your parents are married, that just means your parents found each other first. If you met your step-sis first, and married her, then your parents would be in the same predicament.

I say go for it.