Hi you,
#1. You need to create a variant product with 2 options:
– normal size
– family size
Like our demo: https://demo.leebrosus.com/piizalian/product/fantastic-iron-shoes/
Follow guide at Variable Product
#2. Please copy and paste this css to file style.css ( child-theme):
@media (max-width: 768px){
.wc-pao-addon .form-row {
width: 100%;
}}