Master, where are all the mother/son posts? And I'd love to see some posts involving lady cops on their knees.

There are no genetically related posts at all. Stepmothers are tagged such. Youth is an attractive quality in women and so posts featuring young women will always be more common.

• http://masterlovehurts.tumblr.com/tagged/stepmother
  

Some general “milf” posts:

• http://masterlovehurts.tumblr.com/tagged/milf

There are some cop ones here and there:

• http://masterlovehurts.tumblr.com/tagged/slut-cop
• http://masterlovehurts.tumblr.com/tagged/cop