Thank you for your enquiry.
I am assuming your daughter's husband is of Indian nationality. Your daughter's husband can rely on the exception to the English language requirement on the basis of his medical conditions. He must provide medical evidence to support his application to join/accompany his British wife and child into the UK. If your daughter has special needs and reliant on Disability Living Allowance, carer's allowance or severe disablement allowance in the UK she will also be exempt from meeting the financial requirements under Appendix FM.
Yes there are exceptions to the English requirement and medical illness is one of them. Please rate. Thank you.