How to find a Girlfriend

Hi, Im new, i am 23 years old and i've never had a Girlfriend or even kissed a girl. Its really getting me down because my Step Brother/Step sister have both found partners. My Stepsister has gone on holiday with her partner to greece and my Step Brother is always bringing his gf over to see my Stepdad/my Mum and when they do they always watch movies.

While they are doing that i am upstairs trying to find a girlfriend. I Have tried loads of dating sites but no girls message me back or message me. 

Its really getting me down because i want to be the one who i go on holiday with and bring my gf to meet my mum/stepdad and my dad/stepmum