Beside Windsor are there any other family with a claim to the throne ?

The Windsors are illegitimate German invaders with no claim to the throne.

There are thousands of people in the line of succession, and most are not named Windsor. However most are also way, way down the list.

Yes, too many to name here though, even the Church of England members. There is a long list of them; with names never even heard of before, who are in line.

Barbara Windsor has no claim to the throne.

If Princess Beatrice were to inherit (ninth in line to the throne) her dynasty would presumably be Mapelli-Mozzi, unless, like the present Queen she does not take her husband's name.  The nearest distinctly separate family to inherit would be the Lascelles, the family Princess Mary, daughter of George V married into a century ago, when she became the Countess of Harewood. Any great x grandchild of Sophia of Hanover who is not a catholic is a potential claimant.

Any descendant of the Electress Sophia of Hanover qualifies...and when a Mountbatten-Windsor princess marries, her children take on the surname of their father. Anne's children are Zara Phillips Tindall, and Peter Phillips. Princess Margaret's children are Sarah Chatto and David Armstrong-Jones... there are many different surnames in the extended Royal Family.