What responsibilities do siblings have
Legally, none.
Morality is upto you.
Either the person inherits the entire parents property (or buys the other inheritors share from them, perhaps using a mortgage) in which case they can carry on living there and will have to take over paying all the bills for the property and organising and paying for any maintenance or repairs needed. Or else the property needs to be sold and they're homeless.
If they're homeless they can look for a private rental, they have a job so someone will rent to them. They'll have to accept what they can afford, which might mean renting a room in a HMO instead of having a place of their own. It might mean living in a worse part of town or a different town altogether, if they can't afford to live in the area they're in now. They'll need a bond/deposit.
They may also need a guarantor. This is someone who agrees to pay the rent if the tenant doesn't pay for whatever reason, guarantor is a legal commitment. It means you could end up paying two lots of rent each month, yours and theirs, if they choose to stop paying the rent. Do not offer to be guarantor for anyone you don't like or trust. If they can't find a guarantor then they'll have to use the council homeless route below. Nobody is obligated to be guarantor for them and usually it's foolish to be guarantor for anyone, unless perhaps your own child if you trust them to pay the rent.
They can also report themselves (or be helped to do that) to the council as homeless and will be given temporary accommodation, then eventually permanent accommodation. Temporary isn't free though and can be expensive. As they have a job they'll have to pay it. There's no choice with temporary, you accept what you're given or the council don't have to help you at all. If they're on a low wage they can apply for Universal Credit and might get some to help with living expenses.
Permanent accommodation will be a one bedroom flat and could take years to get, depending on what area of the country they live in. Being homeless and in temporary accommodation does give a person higher priority though.
Social housing works on a bidding system. Their application will be processed and they'll be allocated a banding and some points, depending on their circumstances. Each week they need to log into the housing website and register their interest (which is what bidding is) on a certain number of available properties. In my area you get 4 bids per week. Eventually, they'll be allocated one of these properties, the day that they are the highest bidder. They may need help with bidding. If they bid on unsuitable properties they'll never be given one. Bidding on properties in the correct banding and with the number of bedrooms you need increases the chance of you being allocated that property.
Whether social or private housing, they'll have to obtain furniture and pay for a removal company, unless they have their own car or hire a van and can do multiple trips themselves, with friends helping them to load/unload. There are places to buy second hand furniture cheaply.
If the person can't manage to cope with living alone, report them to adult Social Services and ask for a care needs assessment. They might be allocated a social worker or support worker to help them find a new home and manage their tenancy, help them pay bills, shop for food and organise repairs etc. Social services will tell family they have to do it. It's a lie. Family don't have to look after relatives or help them out at all. So if you don't want to have a relationship with this relative OP, you don't have to, you're not responsible for them just because you're related to them. The only ones you're responsible for is your own children upto age 18, anyone else you help out is voluntary and you can stop at any time.