My registered domestic partner opposite sex inherited a home and we live in this home together. He has 3 children and I have 1 child. He does not have a will. My question is if he dies can his children kick me out of the home? Do I inherit the home the same as a spouse? Thanks.

Registered domestic partners in CA have the same rights as spouses regarding inheritance with a will or not, and CA is still a community property state.
But keep in mind that the law is still somewhat new and is controversial, and changing.
As of Jan '12, opposite sex couples may establish a domestic partnership, provided one or both partners is above the age of 62, and one or both partners meet specified eligibility requirements under the Social Security Act.
I have no idea what happens if you don't now meet that requirement, but assume nothing changes for you (I just don't want to assume).

Not only do you need to keep an eye on the law, but also discuss this carefully with your partner (hopefully with his wishes being paramount). And his children could tie this up in the courts for years if they are willing to pay enough legal fees.

To my mind there is no good reason for either of you not to have a will.

Registered domestic partners in CA have the same rights as spouses regarding inheritance with a will or not, and CA is still a community property state.
But keep in mind that the law is still somewhat new and is controversial, and changing.
As of Jan '12, opposite sex couples may establish a domestic partnership, provided one or both partners is above the age of 62, and one or both partners meet specified eligibility requirements under the Social Security Act.
I have no idea what happens if you don't now meet that requirement, but assume nothing changes for you (I just don't want to assume).

Not only do you need to keep an eye on the law, but also discuss this carefully with your partner (hopefully with his wishes being paramount). And his children could tie this up in the courts for years if they are willing to pay enough legal fees.

To my mind there is no good reason for either of you not to have a will.

Have to be careful when mentioning community property as a blanket. What that applies to is what is accumulated during the relationship. It does not include what was acquired before the relationship nor does it include inheiritance. Those are separate property from the relationship.