I'm not sure that there's a single Daz3D asset which really depict a mother or even a >30 years woman.
That reflects a lack of knowledge on your part, not reality. The Daz3D store has significant resources for "aging" of characters including these, (this is just a few, randomly grabbed from the Daz3D store today):
You must be registered to see the links
,
You must be registered to see the links
,
You must be registered to see the links
. Other morphing tools can be used to add the effects discussed, like dropping breasts, sagging behinds, etc., like these:
You must be registered to see the links
, and
You must be registered to see the links
. Other sources such as Renderoisty also have assets that can help with this such as
You must be registered to see the links
and
You must be registered to see the links
. Renderosity also has a large collection of middle-aged actors which can be used or modified for originality, as well as Adam Twaites'
You must be registered to see the links
site, which I have used for one of the "moms" in my VN.
As far as out of the box models of women > 30, here is a notable one from Daz3D:
You must be registered to see the links
.