First, choose a surname. Then, say if the number for the next name is 5, use the fifth letter of the surname to begin the next name. Continue this until you've got the whole family.
Below is an example
Last Name:
Willoughby
DH: (4, 6)
Lachlan AlexanderDW: (5, 2)
Arista Rachel
DD/DD: (6, 3)
Lara Renee / (2, 4)
Erica CalliopeDS: (3, 2)
Lazarus AugustDS: (3, 1)
Gilbert GustavDD/DD: (4, 7)
Tabitha Ava / (3, 3)
Ariella IngridAD: (3, 4)
Gillian Lexi
Your Family:
Last Name:
DH: (4, 6)
DW: (5, 2)
DD/DD: (6, 3) / (2, 4)
DS: (3, 2)
DS: (3, 1)
DD/DD: (4, 7) / (3, 3)
AD: (3, 4)