In British English it is no longer considered a solecism to use the plurals they, their, them, theirs as a generalized pronoun for words like eyeryone, everybody, anyone, anybody , etc.
( ( ( ( ( ( ( In ( British English ) ) ( it ( ( is ( no longer ) ) ( considered ( a ( solecism ( to ( use ( ( the plurals ) they ) ) ) ) ) ) ) ) ) , ) ( ( their , ) them ) ) , ) ( theirs ( as ( ( a ( generalized pronoun ) ) ( for ( words ( like ( eyeryone ( , ( everybody ( , ( anyone ( , ( ( anybody , ) etc. ) ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (PP (IN In) (NP (NNP British) (NNP English))) (NP (PRP it)) (VP (VBZ is) (ADVP (RB no) (RB longer)) (VP (VBN considered) (NP (DT a) (NN solecism) (S (VP (TO to) (VP (VB use) (S (NP (DT the) (NNS plurals)) (NP (PRP they)))))))))) (, ,) (S (NP (PRP$ their)) (, ,) (NP (PRP them))) (, ,) (S (NP (PRP theirs)) (PP (IN as) (NP (NP (DT a) (JJ generalized) (NN pronoun)) (PP (IN for) (NP (NP (NNS words)) (PP (IN like) (NP (NN eyeryone) (, ,) (NN everybody) (, ,) (NN anyone) (, ,) (NN anybody) (, ,) (FW etc.)))))))) (. .)))
It is still a grammatical mistake to use the plurals they, their, them, theirs as a generalized pronoun for words like eyeryone, everybody, anyone, anybody , etc.
( ( ( ( ( ( It ( ( is still ) ( a ( grammatical ( mistake ( to ( use ( ( the plurals ) they ) ) ) ) ) ) ) ) , ) ( ( their , ) them ) ) , ) ( theirs ( as ( ( a ( generalized pronoun ) ) ( for ( words ( like ( eyeryone ( , ( everybody ( , ( anyone ( , ( ( anybody , ) etc. ) ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (PRP It)) (VP (VBZ is) (ADVP (RB still)) (NP (DT a) (JJ grammatical) (NN mistake) (S (VP (TO to) (VP (VB use) (S (NP (DT the) (NNS plurals)) (NP (PRP they))))))))) (, ,) (S (NP (PRP$ their)) (, ,) (NP (PRP them))) (, ,) (S (NP (PRP theirs)) (PP (IN as) (NP (NP (DT a) (JJ generalized) (NN pronoun)) (PP (IN for) (NP (NP (NNS words)) (PP (IN like) (NP (NN eyeryone) (, ,) (NN everybody) (, ,) (NN anyone) (, ,) (NN anybody) (, ,) (FW etc.)))))))) (. .)))