As you can see in my avatar picture, I carry a pair of kayaks. They are 12.0' and 12.5' (hers and mine). they weigh 40# and 45#. I lift them up by their bow lines, till vertical beside the boat, then push down hard, so that when the bouyancy pushes them back up, I can grab the rim of the opening and then rotate the kayak till it is laying along the side of the boat, then I lift them onto a rack that I originally built for carrying a laser, that is above the aft companionway hatch. The bow of my kayak sits on the lip of the upper deck. Her kayak rests, inverted, on top of mine, then they get strapped down.
Launching is easier, as all I do it toss them into the water. That usually gets attention, but rarely more than a few drops of water into the seat.
Getting into the kayak from the swim grid is easy, as the top of the kayak floats an inch or two higher than the swim grid. I have noticed that other folk's kayaks can be way less stable than mine, which seems related to the shape of its bottom. Mine has many molded in channels or chines, which act on steering and initial stability.
Before buying these, I looked at proper sea kayaks, but couldn't find a spot on board that would accommodate their +14 ft length. Then a trip to Coast Mountain sports, where I found a good selection. I tried out a pair of 13 ft, smooth rounded bottom kayaks, but they were still too long for my storage spot and too unstable for her to get in and out without a swim, so back for a different pair. These have worked well. The biggest improvement to our enjoyment of kayaking was to buy better paddles. the ones they throw in with your purchase are heavy. Your arms get tired just from holding them up. We initially bought $100 paddles to get the static weight down a bit, but a few years later bought $200 paddles to get the weight down some more. Now we can go for hours before our arms get sore, as the weight of the paddles is insignificant. Carbon Fibre rocks!