2 dragons

I own a 6 month old bearded dragon would I be able to get another one that’s 3 months old?

Yes , BUT don't house them in the same tank , or in tanks where they can see each other all the time .

The older larger dragon might not be large enough to make a meal of the smaller younger dragon, but it will object to it's presence ESPECIALLY if it is forced to cohabitate in the same tank with it (irrespective of the mix of sexes, but especially if they both males).
The larger dragon WILL :
>> dominate the smaller dragon
>> attack it (it is perfectly capable of killing the it and inflicting horrible debilitating injuries on the smaller dragon ie biting off it's tail, arms or legs)
>> make the smaller dragon fail to thrive because it never gets it's share of UVA , UVB, warmth (best basking spot), or food, and because it will be in a state of permanent terror (of the larger dominant bullying dragon) and always very stressed.

Best housed in their own personal tanks arranged so neither can see each other .

Would you be housing them together?