GF is making me suck dildo

My gf got this hard putty stuff and made a 3d dildo of my little brother huge dick by putting it around his dick and is comparing it to mine. I'm like raging with envy. Everytime I want to fuck my gf, she puts the mold of my little brothers dick on top of my erect penis and laughs. My little dick can fit inside the mold of my little high school brothers easily even when I'm fully erect. His balls are way bigger than mine and his girth is unimaginable. I don't understand how my little brother got the better athletic, intellectual and penis genes...
Anyways, as my girlfriend is currently fucking my little brother, I am becoming even more emasculated. She's making me suck the dildo so that she can jack me off and I can barely fit it in my mouth. How fucking humiliating is that?? On top of that she's making me lick my brother's insole of his shoes and suck on his socks. I taste his foot grime after the gym with sheer envy..