I think the son is his nephew.
I was also thinking that but i also really want it to be his son
OMGGG UR RIGHT
spoiler alert
Damian is his brother's son, he fell in love with his half sister and Damian is their child, but since the duke does not want to continue the lineage of the Taran family he does not want children that's why Damian is the last heir. But of course with the arrival of the FL everything change
This is so cute i cant wait to meet the son also does this mean his whole family is inbred did he have to do that too i hope not