Shaikh Bin Baz rahimahullah said:
“The Sunnah is that he does the Aqeeqah for them even if they are old. He slaughters two sacrificial animals from each one of his sons. Likewise, for the female is one sacrificial animal, like he slaughters a sheep or goat. The animal is slaughtered, some of it is eaten, and [some] is given in charity. This is the Sunnah. If he gathers his family, relatives, and his neighbors, [and eats the meat] then there is no harm. If he distributes it to the relatives, neighbors, and poor then there is no harm [in this as well]. Even if they are old. He does not give the price in charity. He purchases a sacrificial animal and slaughters it. This is Sunnah” .[http://www.binbaz.org.sa/noor/2835]
Shaikh Salih al-Fawzan hafidhuhallah said:
Question: What is the ruling on the Aqeeqah which is slaughtered for an older person whose father did not slaughter for him when he was young?
Answer: “The ruling on the Aqeeqah is that it is Sunnah and it is to slaughter two sheep for a male and one sheep for the female on the seventh day of the newborn’s birth or the days after it. It is a Sunnah and a right upon the father of the child as a form of gratitude to Allah, the Exalted and drawing near to him. It is a way to remove the child from Shaytan and hope for the safety of the newborn and obtain blessings for him/her.
The meat can be eaten, given as a gift, or charity like the Udhiyah. Also the rules regarding the Udhiyah in terms of the age of the animal and being free from defect also apply to it. If his father did not perform it, then he left off a Sunnah. If his father did not perform the Aqeeqah for him and he performs it for himself, then there is no harm in that from what I see”
[Muntaqa min Fatawa Shaikh Salih al-Fawzaan question no. 304]
Faisal Ibn Abdul Qaadir Ibn Hassan