My GGM took in three nephews and a niece whose parents died suddenly. Their GPs would only take the eldest girl whom they treated no better than a servant. My GGM already had 10 children of her own, and a few years later she added two more little boys (unrelated) to her family when their mother died and their drunken father was always beating them. It seemed to happen a lot back then.
I guess when you have a large family a few more don't make much difference. Her 'adopted' children all appeared as 'son' or 'daughter' on the Census so I guess that's how she thought of them and what she told the enumerator. My GF always thought of them as his brothers and sister. She was a remarkable woman, bringing up 16 children in a small cottage! She was also the local midwife (no qualifications except her own experiences), and did washing, cleaning and baking to boost the coffers.
I shall be exploring the 1921 Census this evening.