In most jurisdictions at 16 you could nominate a guardian. Court forms should be available through your local probate court for your cousin to fill out. your mom would have to be given notice of the hearing and can oppose it. An attorney could be very helpful, and yyou may want to contact legal services in your area to get help.
There is a way to do it. I would advise starting at some kind of legal clinic in Puyallup or Tacoma. Here is a link to the Pierce County Bar Associations pro bono legal services website: http://www.tacomaprobono.org/
All the best! It may seem dismal now, but there are steps to take and people who can help.
This posting is for informational purposes only. It is not legal advice, nor does it establish an attorney-client relationship. For more information, please visit www.justinelderlaw.com.
A guardianship will not address issues like child support and custody, or trump parental rights with regard to these issues. Your second cousin should consult with a lawyer and discuss whether guardianship or a third-party custody order would be best. A third-party custody proceeding (also referred to as a nonparental custody proceeding) could result in an order requiring your mother to pay support to your cousin, and a residential schedule making clear they have custody of you. I have attached a link to information about both guardianship and nonparental custody; forms can be found at the Pierce County Superior Court and Washington Courts websites. It would still be a good idea for your cousin to consult with a lawyer because obtaining custody over your mother's objection could be difficult and requires knowledge of the law regarding parental rights.
The response does not constitute specific legal advice, which would require a full inquiry by the attorney into the complete background of the facts and circumstances surrounding this matter; rather, it is intended to be general legal information based on the limited information provided by the inquirer; it This response also does not constitute the establishment of an attorney-client relationship, which can only be established after a conflict of interest evaluation is completed, your case is accepted, and a fee agreement is signed.