Complex sentence: By then, Spanish law already allowed single people to adopt children; thus, a same-sex couple could undertake a de facto adoption, but the partner who was not the legal parent had no rights if the relationship ended or the legal parent died.
Split into simpler sentences: By then, Spanish law already allowed single people to adopt children. Thus, a same-sex couple could undertake a de facto adoption, but the partner who was not the legal parent had no rights if the relationship ended or the legal parent died.