Great story! My sister and I put together a baby size quilt from some pinwheel blocks my Mom made in her decline (akltzheimers). The blocks were recognizable as pinwheels, but very uneven. But, we said, a baby won't care, so what the heck. She put the blocks together, put a border on it and sent it to me to quilt. It was so uneven that it was a real job to quilt!
My son, the 42 year old father of the baby, cried when he opened the package with that quilt. He said it gave his son a link to his Grammy. He claimed he saw his Grammy working on it, but I'm not sure about that part.
I thought he'd like it; so did my sister. But we had no idea how much the quilt meant to him until he broke into tears! My guess is your sister and BIL feel the same thing about your quilt that my son felt about his sons quilt!
Love makes even those quilts that we think are our worst quilts beautiful to the recipient!