Sorting Families on Plp

First product list A1, A2,A3
Product Family A
Second product list B1,B2,B3
Product Family B

It shows on PLP such as in this way;

Family A Title
Family A description
A1 A2 A3

Family B Title
Family B description
B1 B2 B3

How can I change the order of Families?
Ex. I would like to show family B on the top. However magento is sorting as in alphabetical order.

Thanks