Sentences are determined by several factors. The offender's criminal history, the damage done to the aggrieved party, financial loss in the crime are some of what the judge considers when imposing a sentence. First-time offenders notwithstanding, there had to be something more there that created such a hefty sentence.
You need a very skilled post-conviction lawyer to plead this case citing possible "violations of a defendant's Sixth Amendment right to the effective assistance of counsel". You would need to file a motion to vacate, set aside or correct a sentence as provided by 28 U.S.C. §2255 which is essentially a petition for a writ of habeas corpus. It is available only to people convicted in federal courts who are in custody. If it is a state court, you will need to locate the appropriate motion (whatever the state's version is of a §2255) and fashion the grounds to vacate the sentence.
The likelihood that a family member prevails in a reduction hearing is near impossible without knowing judiciary procedural rules. Please interview some attorneys.
https://www.inmateaid.com/ask-the-inmate/my-son-was-a-first-time-offender-he-plea-guilty-toaggravatedassault-20-yrs5suspended5-post-release-we-didnt-havegoodrepresentationand-didnt-know-anything-about-justice-systemhe-is-noteligiblefor-parole-he-gets-ers-he-has-served4-yrs-of-15-yrs-i-dont-agree#answer
Accepted Answer Date Created: September 10,2015