When it is a second marriage, then there is no 498A. You need to move to the high court to get the 498A case quashed u/s 482 of Cr.P.C
All the more when there are 5 children from the husband's first marriage and 2 children from the wife's first marriage, the question of 498 A does not even arise.
all the more since your father was living separately with his second wife and away from the children from first wife, there is NO SHARED HOUSE HOLD.
A 498A case survives only if there is a SHARED House Hold. In the absence of a shared house hold there is no question of 498A.
Supreme Court in the case of Pawan Kumar Vs. State of Haryana, AIR 1998 SC 958 has cautioned the Courts to act with circumspection. In the words of the Supreme Court "often innocent persons are also
trapped or brought in with ulterior motives and therefore this places an arduous duty on the Court to separate such individuals from the offenders. Hence, the Courts have to deal such cases with circumspection,
sift through the evidence with caution, scrutinize the circumstances with utmost care.
The Judgment o Gaurangbhai Avinashbhai Vyas vs State Of Gujarat & on 16 April, 2015 can be help for you to understand the approach of the various courts in treating false 498A cases
Hope this helps.