If the aqeeqah was not made by the parents and one wants to do his own aqeeqah, would it be correct if he made the intention whilst he did the qurbani or he would require separate slaughter? 

In the name of Allah, the most Beneficent, the most Merciful.

Answer

The performance of aqiqah is highly encouraged.  It is to be performed by the parents or the guardian of the child.

The Prophet of Allah Sallallahu Alahi Wasalam has said that a child is pledged to its aqiqah which is sacrificed on behalf of the child on the seventh day when it is given a name and the hair is shaved off its head.  (Sunan Tirmizi p.278 v.1)

Aqiqah should be performed on the seventh day of the birth of the child and if not done on the seventh day then whenever it is done, it should be on the next seventh day and so on.  (Ibid)

One can do aqiqah even though the child has reached puberty.  (Ahsanul Fatawa p.536 v.7) Similarly, scholars like Molana Anwar Shah Kashmiri is of the view that aqiqah can be done even up to ones death. (Faidhul Bari p.337 v.4)

Regarding your situation, you can perform an aqiqah but it has to be separte from the Qurbani share. For example, if you are sacrificing one sheep for Qurbani, then it is desirable to sacrifice another two sheep’s for aqiqah. (You can suffice on one as well) If you are sacrificing a cow or camel then as it is permissible to have up to seven shares in a cow or camel then you could allocate one share for the Qurbani and one for the aqiqah. (Kifayatl Mufti p.242 v.8)

Only Allah Knows Best

Mohammed Tosir Miah

Darul Ifta Birmingham