As High Flier says, it depends on what choices are available to you and what choices you make at retirement.
Some possibilities: -
At retirement, you buy an annuity (guaranteed pension for life) - you can choose at the time to buy one that has a guaranteed minimum payment period (usually 5 or 10 years) whether you're alive or dead. You can also choose an annuity with dependent's pension built in.
At retirement you buy an Approved Retirement Fund (ARF) - any unused fund gets passed on to your estate, with different tax treatments depending on your relationship with the receipient.
You die before retirement with a Defined Contribution scheme, Personal Pension or PRSA - The value of the fund passes to your estate.