@Gossip_Writer_Clace
I need to see some drama like maybe, in reality, the reason Clary's dad left was that Jonathan wasn't his child and instead was Sebastian's. That could literally be the reason why Sebastian is spreading these rumors to hide the fact. Or you can also have Jocelyn like hate clary later on because she had the love relationship she could never have which is why she could have had sex with Sebastian and why she could have told Sebastian to spread rumors about clary.