How do my husband and I go about getting custody of his 8 year old daughter?

He petitions the court of jurisdiction (either where she lives now or where the original court order was issued) for a change of custody. You state your case, the mother states hers.

Be aware though, custody changes are rarely done if both parents do not consent if there are not severe grounds, such as abuse.

My husband and I want to obtatin custody of his 8 year old daughter. Her mother is always claiming that she has cancer or is going through chemo and radiation (this has supposedly been going on for the whole 6 years since they seperated). Now my step daughter has come us telling us how her mother yells and screams at her when she doesn't clean her room, that she is responsible for washing the dishes, folding the laundry and babysitting her 10 month old sister and changing her diapers while she is home. There have even been times when I have dropped her off and the baby is awake in the kitchen chair in her infant carseat and her mother is asleep in the living room on the couch. Is this enough to gain sole custody of her? Oh and she is always saying that she not to be driving because of the medication that she is on ( she also claims to have seizures).

Frankly I doubt if its enough to wrest primary custody from the mother, but that doesn't mean you shouldn't try.

File in your local Family Court for a modification of the custody order. The judge will probably listen to the daughter's preferences, but, at only 8 yrs old, will probably not give it a lot of weight.

P.S. I merged your two threads and moved them to the Family Law forum. This is a legal issue not a child issue. In the future, please do not start new threads for the same issue. If you need to add more info, then post a reply to the initial thread.