My question involves real estate located in the State of: California
Elderly female adult has been living in mobile home since May 2004. Elderly female's mother and her brother were listed together on the title in 1999 as tenants in common or. Brother had a meeting with Sister, and agreed to "sell" the mobile home to Sister for $5000 in July 2004 when their mother became ill and had to be placed in hospital and then a nursing home. Sister had 2 witnesses present at this meeting, her son, who has also been living with her since this time, and a person unrelated by blood or marriage. Sister, her son, and witness all believe that the "sale" would be honored in good faith.
Brother received the $5000 and cashed the check. BUT. Brother never "got around to" changing the paperwork over to reflect that his sister was the proper owner based on their agreement. Sister kept asking him to fulfill his end of the bargain and fill out the paperwork, but it never happened. Now, in May 2009, brother claims that although he took his sister's money to cement the deal of transferring ownership to her that he refuses to sign the property over to her, and he is going to break into the mobile home and change the locks, evict her and her son formally, sell the property, and leave the state, and leave her to the mercy of DPSS.
Sister has been paying the property taxes for these 5 years, as well as all utilities. She and her son have been in exclusive possession of the property, brother does not have the keys to enter the mobile home. There exists no rental agreement between Sister and son and Brother, nor did Sister or son ever sign a rental agreement with the mobile home park. The mobile home park, however, has consistently accepted rent checks from Sister and son and cashed them. Brother has not before this time objected to Sister and son living in the home. Now, though, in pursuit of selling the property, the brother not only verbally threatened his sister, he verbally threatened the son AND workers at the nursing home, so the situation is definitely hostile.
One complication, Sister has been in a nursing home herself for the last year, but her son has continued to live on the property with the overarching belief that his mother owned the property because Brother took the money.
It seems to me that this may meet the criteria of adverse possession, and if Brother doesn't want to finish what he started and complete the paperwork to transfer title of the property that Sister should be able to file to ask the court to clear title and allow title to pass to her.
If this is true, is it difficult to file such paperwork by oneself to petition for transfer of title by adverse possession?
Any thoughts on this matter would be appreciated!

