I'm sorry for both of your losses 
I'm going to echo many other posters' comments regarding insurances and the practicalities of keeping a second home so far away from where you live.
You can get cover for holiday homes which is more expensive than standard home cover but not horrendously so. However, you'll find that this cost will increase again if you start renting it out to guests. There are, as has already been explained, various conditions which must be complied with in order for cover to engage; keeping heating on during winter, checking the property on a regular basis (and recording this), minimum security requirements, etc. Don't think this is something you'll be able to get away with not doing, or skipping the odd visit because you've got something on. Renting it out also means organising annual gas and PAT testing, plus other maintainence in addition to whatever initial work is required to bring it up to a rentable state. Realistically you'll need to have an letting agent, which obviously incurs more cost and reduces whatever profit you make from your tenant or guest.
As for the B&B idea, if you have no experience of this sector I would drop this plan like a hot potato. Honestly it's really, really hard graft for very little return. You'll stop seeing the house as your family home and it'll become a millstone around your neck very quickly.
You'll also have to think about how you'll devide time at the property with the other sibling equitably; with two families, two sets of friends (and teenagers, in time!) who will all want to have weekends and breaks up there, when are you going to have time for paying guests? Are you happy that the dates when you'll be wanting to use it (school hols, bank holidays), will also be the times when it'll be most marketable to guests? Have you discussed how you might pay for repairs or maintenance between you?
Please be kind to your sibling; if they were POA before your dad's passing and have now been landed with being the executor (quite an onerous and time consuming task) then maybe they just want to draw a line under that part of their life and look to the future. And that's ok too.
I think that based on the fact that you're worried how to fund essentially 1/6th if the property (with your sibling funding the other 1/6th), then that fact plus the mantainence, fees, repairs and other associated costs just means that this isn't the time for you to be keeping a foothold in this area. But it doesn't mean that you can never go back; you could use your part of the house money to fund a static caravan, or invest it and look to moving there permanently during your retirement.