No, Your imagination does strange things. It doesn't mean anything.
You sound confused, and I don't think that it's all down to the dream
How can a dream mean that you love your Cousin? A dream can't *force* you to love your Cousin; it's a conscious process and not some sort of mental hypnosuggestion that would make you 'feel'. In my neck of the woods, getting involved with your Cousin is out-of-bounds and not something you should really be considering; you appear to be showing interest here and you also seem to be looking for some justification to your thoughts ... which, to be honest, I wouldn't give you.
It's a dream. It's your brain using its downtime to run simulations of possible scenarios so you can see how they might turn out.
It doesn't result from your subconscious thinking "I want to have sex with my cousin", but from it thinking "you know, I could have sex with my cousin - I wonder what that'd be like..." If you dreamt about robbing a bank, would that make you a criminal?
Do you love your cousin?