Yes, however if the capacities are identical you should be fine. It is advisable to use matched ( same manufacturer ) packs.

I normally use identical packs and I've run parallel 14.8v 5000mAh packs to obtain 14.8v 10000mAh equivalents, parallel 2200mAh 11v, parallel 5C 3750 packs, etc.

I've never had a problem.

I use a computer controlled ( Team Checkpoint ) charger with a balancer, to make sure that the packs are charged to the same level as well.