Doubling Up For Daddy by Magnus Thorne 

🩵 Taboo (🩸 father/son/uncle)
🩵 Father's Day theme
🩵 Transmasc MC
🩵 Size Difference
🩵 Age Gap
🩵 Established Couple adding a Third
🩵 Erotic Novella
🔥 Dirty Talk, Praise Kink, Daddy Kink, Spit Roast, Double Penetration, Mild Spanking, Mild Degradation, Mild Voyeurism

Overall:    ⭐⭐⭐⭐.5
Spice:       🌶️🌶️🌶️🌶️
Humour:  🤭
Intimacy: 🫂🫂🫂
Angst:      🥺.5

First person dual pov 👀

CW (from author): Explicit sexual content, consensual incest, unprotected sex. The trans MC uses cock, dick, hole, and slit to refer to his genitalia.