Sex of newborn kitties

Question
How can I determine the sex of new kitties?  They are just over 3 weeks old.  Also, how do I introduce them to my 3 adult, outside, altered cats?  The new kitties will be living outdoors also when they are older.  At what age do you suggest I move them and mommy outside to be on their own with the others?  We have several cat houses and sheds where they can get shelter.  At present, they are happy on my enclosed back porch, but I have to depend on a litter box and I am really anxious for them to mingle with the other cats, one and two years older.  This is a
3-generation cat family, 10 in all.

Answer
Hi Susan,

Lift the tale up of the kittens. You will see the anus. It looks like a big "O". Under that you will see either a little "o" or a line. The little "o" is a male and the line is a female. But just to let you know, I have three cats named Diego, Spike, and Toby. Mistakes can be made.  They are all females. =^..^=

Bring the adult cats in to meet the kittens when they are very young. Keep a watch over them. They should be okay with them if they are young enough. Mom will also keep the others in line. If there are problems you may have to use a cat intro protocol.

I don't like having cats outside. Here's a link why. http://www.nitewindes.com/InorOut.html
I can't really give advice on that.

Good luck on your extended family. Think about moving them in.

Ciao, Karen