Legal Question in Family Law in California

She is wrong, she does not have any right to prevent you from seeing your kids, however, it is obvious that she is filing for divorce, you should get an attorney soon, get an OSC, move for joint legal and physical custody ASAP.

You can't force your way into your in-laws house, and you don't want a public confrontation on the record. It takes very little as far as an altercation for you to get slapped with a restraining order, and that is an automatic black mark when it comes to deciding contested custody. Her keeping the children from you is also a big black mark on her, so put up with it while making documented polite requests to see your kids, and in the meantime get into court immediately with a divorce petition and emergency motions for custody to you. I strongly recommend you have a lawyer if you are going to have a contested custody case. Men tend to make all the wrong moves when it comes to the Alice in Wonderland world of Family Court custody proceedings, and as a result get slammed if they don't have an attorney to guide them through it. Right now her conduct will make her look bad to the court. Get good advice and guidance on how to keep the high road and get your kids back through the court, not self-help.