If my brother developed schizophrenia as a teenager, does that mean i will too?

Maybe: Schizophrenia does have a genetic component. But, environmental factors do also play a significant role. So, having a sibling with the disease may increase the risk, but this definitely does not mean the risk is certain.

Chances are higher : Schizophrenia is a brain disorder that for most part genetic but inherited in a complicated/ multifactorial disorder. General prevalence is less than 1% but as sibling your risk goes up to 6%. You or your siblings might inherit some other minor cognitive deficits. If you are past early 20s the chances of developing schizophrenia decrease significantly. Relax chances are low.