From left to right, the arrangement in which everyone will appear the same height is:
Pup, Bro (striped shirt), Dad (red shirt), Mom (blue top), Sis (orange top).

Imagine that the holes are numbered 1 through 5 from left to right.   The family members are shown as having segments that represent units of height.   In the first picture, 8 segments of Mom are showing; let's assume she is 9 units tall, in which case hole #1 is 1 unit deep.   (Only the relative lengths and depths matter.   The solution will be identical if we assume that Mom is 12 units tall and hole #1 is 4 units deep, etc.)   Since Mom projects 8 units above hole #1 and only 4 units above hole #3 in the second picture, hole #3 must be 1 + 4 = 5 units deep.   Sis stands 2 units above hole #3 and 5 units above hole #5, so hole #5 is 5 -3 = 2 units deep.   Dad sticks out 8 units above hole #5 and 6 units above hole #4, so hole #4 is 2 + 2 = 4 units deep.   Pup stands 2 units above hole #4 and 3 units above hole #2, so hole #2 is 4- 1 = 3 units deep.   So from left to right the holes are 1, 3, 5, 4, and 2 units deep.

The heights of the family members are their visible lengths plus the depths of the holes.
Mom 9 units tall, Bro 8 units, Sis is 7 units, Pup is 6 units, and Dad is 10 units.
To make everyone appear the same height, Pup (6 units tall) is in the 1-unit hole #1, Bro (8 units) is in the 3-unit hole #2, Dad (10 units) is in the 5-unit hole #3, Mom (9 units) is in the 4-unit hole #4, and Sis (7 units) is in the 2-unit hole #5.

Here is another way to solve it:
From the first picture,
Mom = 8 units above ground
Bro = 5
Sis = 2
Pup = 2
Dad = 8

From the second picture,
Mom = 4 units above ground
Bro = 7
Sis = 5
Pup = 3
Dad = 6

Comparing the same people in each hole,
M = B + 1
B = P + 2
S = M - 2
P = D - 4
D = S + 3

Solving simultaneously, you can express everyone in terms of Pup:
P
S = P + 1
B = P + 2
M = P + 3
D = P + 5

Then using some logic, you can determine the depths of the hole and where each must stand.