if you lived together fot 48 years and never remarried can you collect social security of theirs?

Hi. You can't actually collect someone else's Social Security benefits, but you can potentially qualify for auxiliary or survivor benefits based on someone's Social Security record. However, you can only qualify for spousal, divorced spousal, or surviving spousal or divorced spousal benefits if you have or had a legally recognized marriage, or a domestic relationship that is recognized as the equivalent of a marriage under state law. Living together in and of itself does not make a person eligible for Social Security benefits on the record of the person with whom they live(d).

Social Security recognizes state laws when determining whether or not a person had a legally recognized marriage. Those rules vary by the person's state of residence, so the best way to find out if you're eligible for benefits would likely be to file an application with Social Security. That way you'll receive a formal determination of your eligibility that also affords you with appeal rights.

Best, Jerry