We stayed as a family of four (2 adults, children aged 6 and 7) and it was perfect for us. Great location to walk around Madrid.
Top tip: there is an amazing ice cream couple of doors away called Mistura ice cream. My children could be coaxed out of the flat after a long day walking and exploring for ice cream and once out they forgot their tiredness as the location meant there was always something fun going on in the evening