It's hard to tell from the pictures. In livebearers the males have a modified fin underneath called a gonadopodium which they use to transfer sperm into the female. Compare your fish and see if any have different fins the gonadopodium is a long stiffened fin. Females don't have them.
Female guppies are usually bigger than males so the big one is probably not male if that helps. As these are young fish you need to use cues like these to sex them.
In the first picture are 3 generation, the bigger one, the in between ones (which are all males) and the fry.
Actually he or she is exactly the same size as the other ones from that gen except that she/he never shows her under fin and it kinda looks like a ...
I thought I even saw him flirting with me other adult females hence why he is in the male only tank now.
But yes, it is very hard to tel hence why i'm here.
They look mostly like females to me. Males stay smaller and the gonadapodium is like a stick shaped fin under their bellies. Females have a triangle fin in the same spot, and usually have more rounded bellies, less color, and are bigger.
Males also have their chest more sticking out right after feeding instead of just having a bigger entire body by the females.
That is why I'm still in doubt about the little one (with the arrow) it looks like a male if you look at the belly, and also smaller than the other females of that generation.
The males didn't help either, they just wanna ride everything I throw in there... *sigh*