Introducing New Kitten to Resident Kitten?

I have a 9 week old male kitten that I have had for two weeks and I just recently brought home a 5 week old female (the grey kitty). The female was found on my aunt's ranch and the mom and the rest of the litter were killed by a coyote.

My aunt rescued her and I took her home once she was off the eye dropper and eating kitten food. Since I brought home the new kitten the male whines when we try to pick him up; he never use to do this. He also became more distant and won't come up to us like he use to. Now when we pet him he usually runs away and he isn't getting along with the female very much. He hisses at her, bats at her, and is relentless when it comes to tackling her. It seems as if he is constantly worried about what she is doing.

Luckily his hissing has been getting better now and he really only does it when she is around his food when he is eating. But his behavior makes me feel like he distrusts me and my boyfriend. Like he is mad at us for bringing her home. Is this something that will go away? Does he hate us? Is is possible that he will go back to being as lovey and cuddly as he was before we brought her? What can I do to help him? What can I do to get him to trust me again? Is he just acting like this because he is "growing up"? Please help me. I am really worried and want to do everything I can to help both of them. I appreciate any ideas or suggestions!

By Selina C. from Billings, MT