1)
Why does it say "Shishah"? The verse lists only five!
1.
'Rashi': There is a reason for this
1
. Also below (25:3) it lists five Bnei Yedusun, and says Shishah!
2.
Malbim: Shechenyah raised Shemayah's children (his grandchildren), so they are counted together with Shemayah.
1
I.e. to count the father with his sons. (PF)