Family said JV was a friend of GD's father. So, Michael's sister's father-in-law.
If the reports about drug dealing are true, I'm wondering if T&M had possibly bought from JV in the past. Money got tight after the trailer burned down, or Mike promised his pilot skills in exchange for drugs. JV comes to collect on Father's Day, possibly hearing about Tina's inheritance. Mike refuses to pay or ferry drugs for JV. JV then either makes them leave that night or catches them as they are leaving in the morning.