Cohabitation is never a good idea, one dragon will be more dominate and can even injure or kill the other (this is why you see dragons missing toes and tips of tails)... they are solitary animals. In housing a male and female together,when adults, your female will be harassed and overbred. I would strongly suggest you read this post >>>>
viewtopic.php?f=6&t=154908&hilit=cohabitation And if you intend to bred them its best to house them separately, and when they are MUCH bigger and older, you can put them together only until the deed is done, then you separate them again... Also LOTS of time and money go into breeding beardies...so def do lots of research on that b4 you make the decision to breed. You can also read this post on breeding >>>
viewtopic.php?f=4&t=126455 and def browse thru the breeding section...
Please read thru the cohabitation post and see what a risk it is to house dragons together. I hope youll reconsider and house them separately. And yes at 5 months old your 8 inch beardie seems pretty small.. And a 2 week old beardie cant be but what 4 inches? They shouldnt even be selling them at 2 weeks old (or be able to say its a male, thats pretty small to try to sex). If you house them together now, your female will most likely dominate the small male, he will get hurt...or possibly die. Shes at least twice his size. She may even try to eat him. There was just a post a few days ago where a bigger dragon ate a smaller one in the er section>>>
viewtopic.php?f=45&t=177653&hilit=something+happened.. And that was a 3 month old eating a hatchling. So def a bad idea putting them together...
For your 5 month old being so small... Did you just get her? or have u had her 5 months? If u just got her is it possible shes 5 weeks? Lots can factor into their growth, feeding, lights, temps...etc.. So if youd like to tell us about ur setup and feeding schedule we can probably give u some pointers to get ur little ones thriving