The Quranic Ayaat are clears about the Usary being Haram but the children after becoming major have to refuse to share Usary income of parents and do something to earn themselves.they can reguse to share inhertance of Haram portion.All my clarification is based upon the non permissiblity of
Usary which clearly support my point but I don't understand as to what more I have tell you except
quoting the Aya:----
يَا أَيُّهَا الَّذِينَ آمَنُواْ لاَ تَأْكُلُواْ الرِّبَا أَضْعَافًا مُّضَاعَفَةً وَاتَّقُواْ اللّهَ لَعَلَّكُمْ تُفْلِحُونَ
3:130 O you who have believed, do not consume usury, doubled and multiplied, but fear God that you may be successful.