Social Security Questions? Ask a Social Security Expert
His ex-wife is not eligible for social security benefits on his working record because she was re-married - but might become eligible if her second marriage ends.
His children will be eligible for social security based on his working record.
You may be eligible for survival spouse benefits if you are considered as married based on your state law - thus if your state recognizes the common law marriage - you would be considered legally married and would be eligible for survival spouse benefits.
You need to be married at least 9 month to qualify.
Let me know if you need any details or help with application.