What was the size of the previous family photos (not taken with a digital camera, but submitted)?

135 camera means that the film used is 135, and the specific size is that the film width is 35 mm (the full width of the film, including the perforation on the film side), and the photosensitive surface is 36 mm x 24 mm.

there is also 12 film, and there are three kinds of photosensitive surfaces of 12, and the three specifications are: 6 x 7 mm; 6X6MM and 6X45mm

You should say the size of the photo, because the photo was developed on the basis of the negative, and it may be enlarged, so it is impossible to judge the size of your old photo.

But if it's a color photo with 135 film enlarged by an automatic developing machine, the most common one is a 5-inch one.