Returning UK Citizen & access to NHS for free

I have been out of the UK for over 10 years. I have returned to the UK to take up a new job. My wife & eldest (step) child are in UK on Settlement Visas, my other 2 children are UK citizens.

Can anyone help me with answers to three questions please:

1) I understand that I have to be "ordinarily resident". Does the fact that I have returned to take up a new job in the UK mean that I am now immediately Ordinarily resident? IF not how long do I have to be here for that to apply.

2) If I am ordinarily resident, do my two young children (UK citizens) count as Ordinarily resident?

3) Does the same apply to my wife & step child who are on settlement visas?

Thanks