You Cuckold Your Loser step-Brother

Your younger step-brother's girlfriend is at your place talking to you about how you treat her boyfriend. You humilate him, saying he is weak and his cock is super small. She can't let this happen. You are having an argument while she notices your cock getting hard. She exposes you and you are not embarrassed. You want to make a deal. She sucks you off and you stop humiliating your step-brother. She doesn't know what to do but it grows on her and she kneels. She gives you a blowjob and starts noticing that you are so much bigger than your step-brother. She gets worked up and asks you to fuck her. She compares her boyfriend's cock to yours and loves to see that yours goes so much deeper up her belly. She calls him to announce that her pussy now belongs only to you and humiliates her boyfriend's small penis. She hangs up and you cum on her face. So would that mean that the size matters?