first assumption i have is that the family member has offered to pay you for the work. and it's important to remember that it
is work. i did commissioned quilts in the ninties. i had a few professional seamstress acquaintences & friends. got the hourly rate they charged ..higest was 13$/hr. so i charged 10$/hr. i kept notepad at machine & logged starting & stopping time as i worked on customer quilt & also did what mommies do for busy young son. most of my work was sometimes done in middle night after busy son finally asleep. i charged for fabric prep time & 6$, sometimes more depending on intricacy of design (i design my quilts). they purchased any fabric. i preferred to go with client for fabric purchase to make sure adequate amount & reasonably attractive together color choices. it was always a fun shopping trip for both of us!
my clients were always pleased with finished quilts. one client even added several hundred dollars to agreed upon price after visiting and seeing almost completed quilt. i know this is more info than needed for simply setting blocks in a sashing ..sewing all together, quilting then adding binding, but it
is work. your personal time used for someone elses project. and i personally know that some nonquilter family members do
not understand the amount of time, knowledge & talent that goes into making a quilt ..even if all you're doing is setting blocks (which need to be squared so that all uniform, repaired sometimes if vintage) etcetcetc. be fair to yourself or let them take it to a professional seamstress & find out the real world cost of their "simple" project.