FH just got off the phone with his father about a misunderstanding on this. Grandfather's dad was senior and died years ago, grandpa is a junior, and FFIL is the third. We asked several times to clarify what to write, and were told to put JR. for grandpa and III for dad.
Dad found out that we put JR. for grandpa and just screamed at FH for an hour about how if the Sr. dies, the Jr changes to Sr, but the third stays the same. Grandpa always told us it was Jr. Aside from FH now being very upset at his dad (which is nothing new), now I'm more confused than anything making the seating chart labels.
The men of my family are the same, but they all kept their labels. What's the point numbering your kin if you keep moving them up anyway? You'd lose count! 
Should I just follow what FFIL says? Is there any rule on this, or just go with whatever each's individual preference is? Anyone else have a hierarchy of men too?
TBH, I feel like FFIL is a bit oversensitive and being rude to FH. :/
