The child is part of your household, even if it was temporarily living elsewhere or if you lived with the child at the grandparents' house. A child can also belong to several households, for example, if the parents live separately and the child lives alternately with the mother and the father.
If the child was part of your household last year, you may be able to claim childcare costs or the tax allowance for single parents. If the child was not part of your household, childcare costs and the tax allowance for single parents are generally not recognised.