Softly Softly, you are exceedingly generous.

My instincts seem correct. Morton was Margaret’s child. She has registered the birth, and recorded her own father as Morton’s father (maybe he was) and she has used her mother’s maiden name.
The address is the same as in the 1891 census, where Margaret was living with her father and brother.
John Buston, the father, died later in the same year. Margaret eventually married in 1897 and went on to have a family with her husband Alfred Holmes.