He could be going through puberty already. Everyone is different.
Here is from another site:
"Another development in puberty is when boys gain the ability to ejaculate. The fluid that comes out is called semen. Often the first few times a boy ejaculates, the semen will not have all the ingredients and it will appear transparent. Later the other ingredients add in and the semen will gain its milky or pearly opaque color."
Another site I found said anywhere between age 9 and 15 is normal for males to begin and go through puberty, a very wide range for sure. Several sites said age 10 to 14.
So I'd say your friend is normal, if probably earlier than some of your other friends. Apparently the early starters also finish their growth (in height) earlier, and the later starters can have late growth spurts (in height). It was kind of interesting to read that.
Sorry, I'm not an expert, but it does sound kind of normal. I'll look up some links. Not everyone begins to get pubic hair at 10, but just like girls, some of whom start their periods as young as 8 and others who don't until 14, there is probably a pretty wide range of normal. Will re-post if I find anything helpful.