Hello Rahman....
Section 41a notice deals with notice of appearance before the police.It applies to the persons on whom a complaint has been made or a suspicion exists.
As per your query, it appears the father of the accused is to be summoned to enquire regarding his son's involvement in alleged offence.
So,Police have to summon the person who are acquainted with the facts of the case under section 160 of Crpc for enquiry.
Now, as per your query....
whether a 93 years old person can be summoned to the police station for investigation...
No...
The section says,The police cannot summon the person who is less than 15 years and above 65 years, a woman or a person with disability or unsound mind.
The police have to go the house or place of such person for enquiry.
In your case, It can be challenged. You can file a writ before the Hon'ble Highcourt.