Let explore two extreems here. I guess you are worried here is either there is something clinically or psychologically unusual here.
Clincally speaking, one extreem could be having genetic makeup of a boy but appearance of a girl. There are cases like that in the world. These cases come to the surface usually during puberty when the switch happens. Even these children behave according to their appearances before actual switch. This is a rare occurance and mentioed here to put your mind to ease once you have explored this extreme.

During early childhood the gender orientation and behaviour is usually not organic in nature. Its origin is mostly physchological and environmental. This is true in more than 90% of the cases. Like said in the post earlier, pointing it out to the child will have very negative effect for child's psychology for the rest of life. You may cause this anomally by doing it actually. This behaviour will self correct at or before puberty.

You should also know that in some cultures there are things which are normal for them but may make you raise your eye brows. I am male and grew up hugging and kissing and holding hands of my male friends, a behaviour can be easily catogorised as gayish in the western world.

In a nuteshll, there is either nothing to worry about it or if there is anything in the rarest possibility then you can't do anything for it :)