If you absolutely have to use one of those it would have to be 'themself'. 'their' clearly is wrong in that place because it's possessive pronoun. The reason w

If you absolutely have to use one of those it would have to be 'themself'. 'their' clearly is wrong in that place because it's possessive pronoun. The reason why 'their' can be used in the same position in the sentence is that it's used as a modifier to the object, i.e. the position in the sentence is the same but the syntax tree is different.