Immigrationboards.com

I came in UK under Tire -2 General, 5 year route, entered on 21 May 2014.

My son entered in UK as dependant (with his mother) (8 yrs old, date of birth 06 May 2009) on 07 Feb 2015,
Went abroad: 26 Jan 2016 to 18 Feb 2016
Again out of UK from 09 April 2016 till now - which will be almost a year continuous absence.
He is expected to be back in UK (with his mother) – April May 2017

Will he get ILR together with me when I shall be eligible?

There is no absence limit as such for children but obviously, they should be living in the UK to qualify for ILR and not living abroad for the qualifying period.

Was the child born in the UK or abroad?

Generally children born abroad have the same visa status as that of the less-privileged parent.

So, the child will be eligible for ILR with the mother, as she is on a dependent visa and entered the country later than you. The child can be registered as a British citizen when at least one parent has British citizenship and the other is applying for British citizenship.