Mum die before my stepfather ,we are now adults looking to see if we can claim on their or his estate 5 they were married for over 30 years and were still married when both died no will was left and he didn't have any other family ,no blood relatives we were his family .

ANY question on law needs to include your general locale as laws vary by area.

If mum died before him, then he inherited from her according to the applicable laws of inheritance. Since her children are not his relatives, then you probably have no claim on his estate. But you may have a claim on a share of your mothers estate.