This apartment is fabulous! We stayed here with 3 young boys (all under 4) and for a family seeing Istanbul it was excellent. Good location (though all the hills and stairs around the apartment made for loads of fun with the pram) near Taksim Sq but also so close to the tram that takes you straight to all the tourist sites. Apartment pretty basic but all you need.
Yesim as per previous guests remarks is really great. Helped us out loads with tips and advice as well as the airport transfers.
All in all a great place to stay. Highly recommend it to anyone wanting to see Istanbul