I was divorced in Ohio Yrs ago and I live in California. I now have both my children as of October. My daughter already lived with me for 3 yrs, but my son just moved with me in October. Can I file for a change in custody in California or do I need to file in Ohio. My current cusody agreement is in Ohio, But it would be nice if I could file in California

Link to California Family Law Code'

http://www.leginfo.ca.gov/cgi-bin/calawquery?codesection=fam&codebody=&hits=20



This code my help,

FAMILY.CODE
SECTION 3421-3430



3421. (a) Except as otherwise provided in Section 3424, a court of
This state has jurisdiction to make an initial child custody
Determination only if any of the following are true:
(1) This state is the home state of the child on the date of the
Commencement of the proceeding, or was the home state of the child
Within six months before the commencement of the proceeding and the
Child is absent from this state but a parent or person acting as a
Parent continues to live in this state.
(2) A court of another state does not have jurisdiction under
Paragraph (1), or a court of the home state of the child has declined
To exercise jurisdiction on the grounds that this state is the more
Appropriate forum under Section 3427 or 3428, and both of the
Following are true:
(A) The child and the child's parents, or the child and at least
one parent or a person acting as a parent, have a significant
connection with this state other than mere physical presence. (B) Substantial evidence is available in this state concerning the
Child's care, protection, training, and personal relationships.
(3) All courts having jurisdiction under paragraph (1) or (2) have
Declined to exercise jurisdiction on the ground that a court of this
State is the more appropriate forum to determine the custody of the
Child under Section 3427 or 3428.
(4) No court of any other state would have jurisdiction under the
Criteria specified in paragraph (1), (2), or (3).
(b) Subdivision (a) is the exclusive jurisdictional basis for
Making a child custody determination by a court of this state.
(c) Physical presence of, or personal jurisdiction over, a party
Or a child is not necessary or sufficient to make a child custody
Determination.

Hi, Hopeful,
Another good source of information is your local Court House. You could either call, or go see, the person in the Court Clerk's Office. That is where all records are kept, and where filing something for the Court's consideration takes place.
They should be able to guide you, if you don't have a lawyer to advise you.
I do wish you the best of luck.