If hired commercial surrogacy is considered wrong because there are business involved. They may take the child do what we don't know.
Some families do not have children naturally. Because have health problems But Want to have a child by a Carries merit is not wrong if surrogacy by relative. And do not hire
If surrogacy by relative is not wrong if the sister can't have children. But want a child may provide pregnant sister instead. It does not have problem
If hired pregnant instead, irrelevant by blood is considered wrong. Because no different to human trafficking.
Some people want to have children but cannot have. surrogacy by relatives not wrong because they want to have children, but there is not.