Needing Help

So about 6 days ago my mum and step-dad got married but I can’t stop thinking about my step-dads nephew , only problem is I’m 14 and he’s 20 so I don’t think he will feel the same , but is this weird? Also... I’ve literally been thinking in my head like when I’m 18 he’ll be 24 and we’ll both be together and it’s driving me crazy!