What is the ruling on the second عرفي (customary) marriage of the sister's husband, which took place without her knowledge or consent while she is pregnant and ill, and what is the ruling on his spending on the children of the second wife equally with his own children, knowing that local law requires the first wife's consent to complete a second marriage?

Allah has permitted a man to marry up to four women, provided he observes justice, and is able to provide for their maintenance and housing. The validity of a man's second marriage does not require the approval of his first wife. Furthermore, the husband is not obligated to financially support his wife's children, except as an act of charity and kinship. It is advisable for the wife to assist her husband, treat him with kindness, and fulfill his rights.