FlyerTalk Evangelist
Join Date: Oct 2004
Location: MUC/LAX/SMV
Programs: LH, UA, BD, AA, NW, FB, NH, AC, Sixt, Hertz, Avis, *W, HH, Marriott, PC, Leaders Club, AMEX
Posts: 12,406
IME, some people simply don't want to feel indepted. In this case, the BIL might have felt that he needed to "repay" the OP somehow during the vacation (like paying for dinner, sightseeing trips etc.), and he simply didn't feel it was worth it in this case. So not taking the upgrade (especially as he thinks it's basically a waste on the kids) gives him peace of mind and he can enjoy the vacation without thinking about ways and means to "repay" the OP.