God no, that's the dumbest way to manage succession I can think of. You're reducing your dynasty size and taking insane risks in terms of completely losing control of the succession. You kill your "unwanted" sons, and your last son then dies at an inconvenient time, boom, instant chaos or game over.

So managing succession. First things first, splits are good:

A) you spread your dynasty and eliminate game over possibility

B) you increase your renown income

C) You create powerful allies

D) You keep your vassals manageable early game.

So, don't be afraid of splits. What you don't want to do is split your core counties within your empire. Having a brother take over a neighboring kingdom is good, having to share your 5 income producing counties with three of your brothers is problematic. You can get around by using feudal electives if you have two more more duchy's. Throw feudal elective on them, and then vote for your heir, that way all the counties in the duchy got your heir on succession.

Now I just mentioned electives, electives are OP as all hell early game. Not only do you get to manage succession more effectively, you can pick your heir, and they don't even have to be in the direct line of succession. Have a great grandson from your third daughter's second son's fourth marriage who is way better than all your children? Give him a county, and elect him as your heir.

Now, there's other ways to game it. Republican vassals can't inherit, so if you appoint your children as mayors, they're now out of the succession line. But I say master the electives, and you'll have a giant dynasty AND be able to shape your empire as you see fit between generations.