Hi Sammie. Unfortunately, for the odd person, repeated plucking of the eyebrows leads to the hairs just seemingly giving up and never growing again! After 3-4 yrs, I would suggest that what you have now, is the final brow formation!
There are two recommendations .
One is to become a dab hand with an eyebrow shadow or pencil.... My own eyebrows are pretty scrawny and I use a brow shadow, thereby making them seem pretty lush and shapely! Customers at my salon are always asking to have their eyebrows "like yours!" It does make me laugh.
Secondly, you could have them permanently made up. For all intents and purposes, you would have them tatooed in. Of course, you would need to find a good 'artiste.' On the off chance that you are near Liverpool, I could give you details of a very good specialist in this area. It costs roughly �250 and lasts 3 yrs, so worth it as a more permanent solution.