There is no law addressing this specific issue so it must be addressed in the court orders.
It's dependent on the custody order, but it's not appropriate for either parent to have a live in.
If someone goes to jail the obviously their freedom of movement is somewhat curtailed. Other arrangements need to be made.
Check with your attorney for custodial laws.
The Heavener family come to Mississippi in March 10 1895.
No. It's your child. Your family. Your obligation. Clothes, food, toys, or care, custodial or not, you do not get to "write off" what it costs to support YOUR FAMILY. (And in this case, it's to have someone take care of your obligation so you can do something else). These are what you spend your after tax income on. Oh - the tax you pay...that takes care of them and you too.
If the word FAMILY is used as adjectival predicate ("You are a family to me"), then the opposite would be STRANGER ("You are a stranger to me"). WHAT?
It seems unlikely that a non-custodial relative would have "standing" to request a change in child support.
The opposite of stranger is familiar, or family.
Emmett Till went to Mississippi to visit his family.
* To love someone (this can include family members and friends) is a love of respect for one or more people, but being in love is when you love someone of the opposite sex with all your heart.
You must go to the family court to see about getting the custody changed.
You will need an attorney well versed in family and custodial law. There will have to be a good reason, like both biological/custodial parents being unfit to raise the child.