my father is currently serving in army do i get the benefit of UREX

If you're asking about UREX (Defence/Ex-servicemen quota) in REAP (Rajasthan Engineering Admission Process) :

No, not automatically.

If your father is currently serving in the Indian Army , you may be eligible under the Defence Personnel/Ward category , but it is not the same as the Ex-servicemen category . REAP provides reservation/priority for eligible wards of defence personnel as per the Government of Rajasthan rules, and you must submit the required certificate from the competent authority (such as the Zila Sainik Welfare Board, wherever applicable).