Sydney lines really uncommon?

I've been reading a lot about palms lately, because I have two very distinct sydney lines on both of my palms, I am female so I know it's more common in us (so I've read). However, I started looking at several hands around me...my dad has sydney lines on one palm (the other palm, the headline is a little shorter), my paternal grandmother has sydney lines, my stepmom has a sydney line, 2 of my best female friends have them. Can palm lines be hereditary? I admit I can find more about a single transverse palmar crease than a sydney line...to me it doesn't seem like they are all that unusual. Any experience or comments?