Death of owner of an unregistered property, where the title deeds have been destroyed

My parents purchased their house in the 60's under both their names. My father passed away a few years ago and my mother passed away this year. In the period between their deaths, the deeds were destroyed when the bank storing the deeds removed their safe. The house has never been registered with the Land Registry. The house will pass to my siblings and myself. The house will subsequently be sold.
Can you provide some guidance on the steps needed to get the house registered with the land registry?

Alan - sorry to read of your losses.
See our PG 2 with regards how to register for the first time where the deeds have been lost/destroyed - First registration of title if deeds are lost or destroyed (PG2) - GOV.UK
With regards the deaths and how to then deal with the property see our online assisted guidance - HMLR Guide Page  · HM Land Registry
I have linked you to the guidance where there were joint owners and then a sole surviving owner after the first death. The executor for your late Mother would be the one to then deal with the property re a sale. However as the deeds are lost and there is no registered title any buyer is very likely to insist that it's registered first. Registering it in the name(s) of the beneficiary is the usual way to go in such cases. 
Any first registration will therefore include a copy of your Father's death certificate and Mother's probate