Chances of a Mystic Rectangle?

I'm wondering how frequently these aspect patterns occur. The reason I ask is that both my mother and I have this pattern in our natal charts. The odds of this happening seem rather slim, and it was the first thing I noticed when I looked up her chart.

What does it mean?

Does it mean anything at all other than a lucky roll of the dice?

What is that?

Two trines and two sextiles that form a rectangle in the chart.

I have one: Venus in Taurus XI trine Pluto in Virgo III; Neptune in Scorpio V trine Chiron/Jupiter conjunction in Pisces IX. Venus sextiles Chiron/Jupiter, and Pluto sextiles Neptune.