how did you equate him propositioning you to him getting horny
over his mum?
propositioning you is one thing, but the "age thing automatically
means it also applies to his mum" is something else.
from your description the 19 yo sounds a little disturbed ~ if what
you say about him and his mum is true.
are you so not familiar with people of the oppposite sex that you
must ask this?
if not, then you need to rethink for yourself.
milf doesnt usually cover your own mum lol