Most states do not recognize common law marriages. If you live in a state where that is the case, you are not permitted to file as a married couple. I am not sure what is the applicable law if you do live in a state which does recognize a common law marriage. Do a google search for your state to see if it does or does not recognize common law marriages. The children would not be affected for purposes of SS survivor checks but your girl friend would most definitely be affected if you are married. Survivor checks would end for her - but not the children - if you two got married or if you declare yourselves to be common law married in a state where that status is permitted. It sounds like you would lose more money than you would gain. She probably qualifies for head of household status.
