Not sure if this is the right board but here goes.
Those with moderately disabled (physical and learning) sibling that cannot function living alone but disability is probably not life limiting, what plans have you made with parents for when they are deceased or no longer able to care for them? They are retired and starting to worry about what will happen/ what plans can be made. Although there's a part of me that wants to say we'd just move straight in and take over care we have two young children, parents live a fair way away in a place with v limited job prospects so it would be a difficult move. I don't think they'd adapt well to a big city move so them moving into our v small house probably won't be great especially as we have stairs. I have no idea what suggestions to make. I know it could be years but no way to know what the situation will be when the time comes.