Legal Question in Family Law in California

You could not be held personally liable for supporting your boyfriend's child. However, any change of circumstances such an increase of income or decrease in expenses could be considered when adjusting the amount of support that he has to pay.

The simple answer is "No, you will not be legally responsible for his child support." Child support is and always will be your boyfriend's separate property, and no one will not come after you personally, nor can your income be included for purposes of calculating child support (although you may want to disclose it for tax reasons).

However, your question was whether or not you would become financially responsible for his child support, and from a non-legal perspective, the answer is yes. Child support arrears, or even a wage assignment, affect your boyfriend's credit. It takes away from his monthly income, which you will have to make up with your own earnings. If the two of you choose to have children, there is that much less money to be spent on them. You may be looking at substantial attorney fees should you ever need to adjust child support (or custody/visitation). Even keeping your bank accounts and taxes separate will do nothing to make up for his decreased income.

I'm certainly not advising you against marrying your boyfriend by any means, but you do need to be aware of all of the long-term financial implications. You're definitely taking a step in the right direction by asking questions such as these, and I'm very glad that you're taking this initiative. Good luck!