Complex sentence: Parents used to prefer children from the same clan, but recently the clan or family name is no longer a deciding factor in adoption since it is now legal to adopt a child from a different clan and then to change the child's family name.
Split into simpler sentences: Parents used to prefer children from the same clan, but recently the clan or family name isn't a deciding factor in adoption. It is due that now it is legally possible to adopt a child from a different clan and change the child's family name.