Seeking advice regarding 41 A Cr.PC notices and harassment case.

What is the period to serve 41 A CrPC notice to A-2 & A-3 in a 498 A, 323 IPC case. a case under the above section was filed on [deleted] against A-1 to A-3. After one month of registration 41 a Cr.PC notice was served to A-1 (private employ). But not served notices to A-2 and A-3 till date. A-2 is working in Police department as Head Constable cadre. He shown all the evidences to investigation officer (SI of Police) about their non involvement in the offence. Some of the witnesses also confirmed their non involvement to SI of Police. But now the SI of Police telling that the involvement of both (A-2 and A-3) has comes under 498 A IPC due to the complainant and her parents are raising allegations against A2 and A-3. After a long gap ( 6 months after) the IO trying to serve 41 Cr.PC notices to A-2 and A-3 now. SI of Police also telling that if he did not add their involvement in this case he will suffer with some problems and will face allegations with complainant due to the A-2 is in same department. The IO did not doing justice to A-2 and A-3. what will they do to obtain justice. what is the period to serve 41 A crPc notice to accused. Please give legal advice