Are there any yuri manga where they're also parents? Closest thing I can remember are some Sailor Moon doujins.
Does 1x1/2 count? ;p
But seriously, there's Ohana Holoholo, which is great (but is being translated way too slowly), And Ebisu-san and Hotei-san has (as a side element) the title characters bonding over taking care of Ebisu's niece.