1) you should oppose grant of probate . file your affidavit opposing grant of probate . the fact that will was not disclosed for period of 6 years after your father demise is a suspicious circumstances surrounding the will .
2) you have been wrongly advised by first lawyer that probate should be applied within 3 years only . if there was no dispute between legal heirs it is not necessary that probate should be applied within 3 years only
4) however your brothers would have to explain why they delayed disclosing that will was made by your father for period of 6 years
5) are the witnesses alive ? was your father of sound mind at time of execution of will ?
6)registration of will is optional and not mandatory requirement
6)contact a local lawyer and contest the will if you believe that your father signature was forged or that your father was not of sound mind at time of execution of will or that will was made under undue influence or coercion