Number of dependents query please

Could anyone answer a question for me please?
At what age does an autistic child (aspergers)no longer become a dependant for the purposes of a CSA assessment?
My ex and I had 1 child together. He has remarried & had 2 further children with his wife. His wife has a son who is autistic but lives in residential care, & who will be 19 years old this year.
Am I right in thinking that once he reaches 19 he will no longer be classed as a dependent, whether he is autistic or not?

CSA maintenace is payable only until a child is 19, so your ex''s wife won''t be able to claim via the CSA from her son''s father once he turns 19.

If this son lives in residential care then I would not have thought he would be taken into account in any assesment of your ex-husband''s liability for child support for your child, as he is not a child living with your ex-husband.

I think it is unlikey that the son would be considered to be a ''relevent other child'' whose disability might justiofy a variation of maintenace once he is no longer a child, but you would need to check that with the CSA.

Thank you very much for your reply. I shall check this out with the CSA.
Regards.