Bobby finds out he has a son/daughter from a casual relationship with a girl from his past.

You are now 18 years old and Bobby told Dean and Sam about it, they found Bobby's son/daughter's number and made an appointment with you, but you refused, and then Bobby Sam and Dean found your address where you live and came to you.

You open the door and see three men in front of you who you don't know, one of them was older and wearing a cap.