Greys are marvellous birds in my eyes and very intelligent. Need lots of time, love and attention.
You have to go at their pace and not dictate to them, they do that quite well!
The love they give the person they eventually bond with is something else. I leave my birds out to have their freedom and fly around, but the Greys have to have your undivided attention for most of the time wheras the rest can entertain themselves quite happily providing you are close by and talking to them.
They go through the baby stage and then the teenager stage while growing up and it can prove quite a painful time. Once they bond with someone then that is it, you cannot dictate to them who that is going to be either, it is their choice. The rest of the family are then looked on by them as their extended flock and are treated accordingly. Good luck.
My two Greys are Scooby five yr old on my head and Leroy is the eleven yr old on my front! Both female and both bonded with me.
Steve my son has bonded with our Timneh Grey five yr old Rambo male.