Are you thinking on paralleling power MOSFETs on your design to increase power output?
One much publicized benefit of power MOSFETs (compared to other semiconductor devices) is that it is easy to parallel them to create a group with increased capability.
Although this feature is superficially true, there are several potential problems that you should consider.
I recommend you to read these application notes from different manufacturers:

• NXP AN11599 is well explained and readable.
• VISHAY AN941  is more technical but brief.
• IR technical note is the most technical one.

Good luck!