Lost 😔

When I was 16 my dad married his ex wife who had two kids , boys . One of them were my age the other a few years older. Me and my step brother (of same age) we kind of clicked and we truly fell in love. We never fully committed to each other because we were always afraid that we would be forbidden from each other. But now ever since our parents divorced we've persued  a relationship. Is it wrong for us to be together?? Should we tell our parents were together or wait a little while? My dad has been in another relationship for a few months now and his mom is still single should we wait a little while or tell them asap?