LTVP for Mother-in-law

My husband holds an EP with Salary >15k, while i understand he is eligible for an LTVP for his parents, we are not keen on taking it for his parents, however wanted to check if we can bring in my mom under LTVP category based on my husband's income.  This is because my mom is a widow currently staying alone in india and will need our support to take care of her.  While i hold an EP, i am not eligible for an LTVP (salary <12k).  Can someone suggest if we can apply for LTVP for my mom under a combined salary category of both my husband and myself.
As far as I understand (but please check this with MoM!), in-laws can be invited on LTVP as well.
But combined income is not possible.

@beppi Thank you, will try to get this checked with MOM.

@beppi Hi, my husband had submitted a request to apply for LTVP through his HR which was then referred to an agent, who came back stating LTVP is applicable only for parents and not in-laws.  Just wanted to update the forum on the requirement.

Thanks for coming back to clarify this!
I hope you can find another solution for your mother.