Parents be permitted to use IVF to have a baby

Jodi Picoult's novel “My Sister’s Keeper” brought popular attention to the use of donor siblings. In the book, eleven-year-old Anna seeks the help of a lawyer in hopes of earning medical emancipation from her mother. Anna is being asked to donate a kidney to her older sister, Kate, who has leukemia. Anna was conceived by in vitro fertilization to become a matching donor and has been subjected to multiple medical procedures since she was five years old in order to donate to her sister. Should parents be permitted to use IVF to have a baby as a donor for their sibling? Who should be able to decide how and when the donor child should contribute to help their sick sibling? If the donor child develops a disease, is it acceptable to have another donor child?
To help understand policy related to this issue, here is an example of how a policy statement from the American Academy of Pediatrics was applied to propose policy modifications in the UK: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4228464/

Should parents be permitted to use IVF to have a baby as a donor for their sibling?
Who should be able to decide how and when the donor child should contribute to help their sick sibling?
If the donor child develops a disease, is it acceptable to have another donor child?