Is there a way to find relatives?

my dad had two children before me my dad. both were with different women. my mom says that Dylan is about 19 by now and Matthew is about 12.im fourteen and Tristan(my full brother) is 15. neither of my half brothers know my dad or me exist. im curious of who they are. the last time my mom saw dylan he was three years old. all i know about my brothers are that they look like my full blood brother tristan. how can i find my siblings??????