Is a little confusing the way you set it up. Maybe try a table next time?

I got Family B being the oldest family by ~471.9 years.

Family A math:
x+(X+4)+(x+8)+(x+12)

y+(y+2)+(y+4)+(y+6)+(y+8)+(y+10)

2+5+8+11+14+17+20+23+26+29+32+35

x+12 = (1/2)(y+10)

y=35

1/2(35+10)=22.5

x=22.5+46=68.5

68.5+73+77+81= 300

35+37+39+41+43+45 = 240

2+5+8+11+14+17+20+23+26+29+32+35 = 222

Family A total: 762

Not going to give my answer but plugin from there...

Family B math:
174/2 = 87

87/2=43.5

43.5*grandparents =

87*0.33333333=28.9999999

28.99999*grandkids =

0.8*28.9 = 14.499= 14.5

14.5*children =

12 *5 = 60

Add them together and get your age.

I don't want to show my full work/answers because I encourage others to think for themselves. @Nerdig and I disagree on the answers but this could even be due to a rounding issue somewhere.