It pleased her to see Aunt Maude waiting tables. Smiling to herself, Alice reflected that Maude was materteral ... like a kindly aunt.
2013 October 5, Bee Rowlatt, “Japan's new luxury sleeper train [print edition: Suite surrender on the rails]”, in The Daily Telegraph (Travel), archived from the original on 9 November 2013, page T9:
A materteral lady told me that people come here from the city in search of peace.
The Oxford English Dictionary has materteral and materterine, both derived from the Latin matertera (maternal aunt), and described as "humorously pedantic"; for "characteristic of an aunt". There are two quotations : With maternal and materteral anxiety (1823) and A kindly materterine message (1874).